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The cat with paw or pad problems
53. The cat with paw or pad problems Isobel Phebe Johnstone
KEY SIGNS ● ● ●
Erythema, scaling, crusting, and/or pruritic lesions. Nodules, draining tracts, ulcers and/or abscesses. Distortion of the nails or deformity of the foot.
MECHANISM? ●
A wide variety of diseases can have paw or pad problems as part of more generalized signs, or the lesions can be confined solely to the foot.
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Disease of the feet includes the paw, pads, digits and nails. Interdigital spaces are seldom affected in cats. It is rare for the disease to be confined solely to the feet. Usually the feet are affected in conjunction with other areas of the skin.
WHERE?
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WHAT? The most common problems seen in the paw are: ● Bacterial paronychia from a variety of causes. ● Immune-mediated diseases. ● Nodules or ulceration due to infections or neoplasia.
QUICK REFERENCE SUMMARY
Diseases causing paw or pad problems ANOMALY ●
Variation in number of the digits* (p 1118)
Hereditary variations in the number of digits, generally six toes, occur most commonly on the front feet. ●
Hypomelanosis (vitiligo) (p 1122)
Loss of epidermal melanin is evidenced by non-pigmented patches in otherwise pigmented areas such as the nose, lips, mouth and paw pads. continued 1107
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continued ●
Hyperpigmentation (lentigo simplex)** (p 1113)
Dark pigmented patches (“freckles”) occur in the non-haired areas of orange cats older than 1 year of age. ●
Epidermolysis bullosa (p 1123)
A hereditary claw-shedding disease seen in Siamese kittens causes the claws to shed easily with minor trauma.
METABOLIC ●
Hypothyroidism (p 1121)
Erythematous, scaling lesions of the footpads occasionally occur with hypothyroidism. Seborrhea sicca and a dry lusterless hair coat, which is easily epilated, and has poor regrowth after clipping may be evident. It is very rare in cats, and occurs most commonly after bilateral thyroidectomy. ●
Hyperthyroidism** (p 1113)
Unkempt hair coat and overgrown claws are commonly seen. Systemic signs include weight loss, polyphagia, polydypsia/polyuria and nervous/hyperactive temperament. Usually seen in cats older than 8 years. ●
Hyperadrenocorticism (p 1121)
Rare condition in cats that results in very thin and easily torn skin, especially on the digits. Other systemic signs include polyphagia, polydypsia/polyuria, abdominal enlargement and skin infections. ●
Diabetes mellitus (p 1122)
Whitish, waxy nodules in the paws are a rare complication of diabetes mellitis. Other systemic signs include polyuria/polydypsia, weight loss and polyphagia or anorexia. ●
Calcinosis cutis (p 1123)
Metastatic calcification occasionally occurs in the pads of the feet secondary to renal failure. Affected pads are enlarged, firm and painful. A chalky white-to-pink material may be visible through the intact epidermis. Pads may ulcerate and exude a chalky, white, pasty material.
MECHANICAL ●
Foreign bodies (p 1120)
Foreign bodies may result in nodules, abscesses or draining tracts in the interdigital web. Foreign bodies are much rarer in cats than dogs.
NEOPLASTIC ●
Primary and secondary neoplasia (p 1116)
Neoplasia may cause swollen painful pads or digits that become ulcerated. Various neoplasms have been recorded as having a predilection for the feet; squamous cell carcinoma, metastatic ungual carcinoma, fibrosarcoma and malignant fibrous histiocytoma have been more commonly reported. ●
Cutaneous horns (p 1122)
Cones of hard keratin growing out from the skin occasionally occur on the feet.
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PHYSICAL ●
Irritant contact dermatitis or chemical burns* (p 1119)
Erythema and ulceration of the footpads often occur together with salivation, mouth ulcers and anorexia. ●
Burns (thermal)* (p 1119)
Superficial to deep ulceration on the footpads occurs, depending on the severity of the burn. ●
Frostbite (p 1120)
Frostbite may result in erythema, edema, necrosis and sloughing of extremities.
INFECTIOUS (VIRAL) ●
Feline pox virus infection** (p 1113)
Multiple papules, vesicles, plaques or crusts and ulcers may occur on the face, ears, limbs and paws associated with pox virus. Paronychia and sloughing of footpads may occur. ●
Infectious pododermatitis*** (p 1111)
Viral, bacterial (most common), fungal and parasitic agents may cause pad and paw disease. Bacterial: Paronychia involving one or more claws, and more rarely pyoderma or fistulated interdigital abscesses are usually caused by the more common opportunistic bacterial infections such as S. intermedius and more rarely by the yeast M. pachydermatitis. Fungal: Single or multiple ulcerated nodules, or draining fistulated areas are usually associated with the rare opportunistic bacterial and fungal infections. Pheomycotic lesions are very darkly (black) pigmented. Nonpruritic, erythematous scaling, alopecic lesions are associated with dermatophytes and usually there are lesions elsewhere on the body as well. Kerion (nodular furunculosis) formation and onychomycosis (fungal claw infection) are rare. Malassezia causes brown staining at the base of the nails only, or a more generalized scaly erythematous dermatitis. Viral: Calici virus may produce footpad ulceration in association with oral ulceration, usually without the more classical respiratory signs of sneezing and nasal discharge. Parasitic: Erythematous, alopecic lesions may occur with Demodex cati infections, or pruritic crusting lesions with Notoedres cati. Usually there are lesions on other parts of the body.
INFLAMMATION (IMMUNE-MEDIATED) ●
Pemphigus* (p 1117)
Pemphigus foliaceus is most common. A symmetrical pattern of lesions occurs on the face, ears, trunk, feet and mucocutaneous junctions consisting of erythema, oozing, crust, scales and alopecia. Some cats may present with only foot lesions. ●
Systemic lupus erythematosus (p 1121)
SLE is a multi-systemic disease, which may involve the skin with ulcerative lesions of the feet and paronychia. ●
Plasma cell pododermatitis* (p 1115)
Plasma cell pododermatitis results in swollen and very soft (“mushy”) footpads with normal pad symmetry. Normally it is non-painful, but the pads may become ulcerated. ●
Insect bite hypersensitivity** (p 1114)
Symmetrical pattern of erythematous papules, ulcers and crusts occur on thinly haired areas, especially the bridge of the nose and/or ear tips. Sometimes the footpads are also affected. Lesions have a seasonal occurrence. continued
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continued
ALLERGY ●
Atopy and adverse food reaction* (p 1116)
Atopy or adverse food reaction may just involve the feet with nail biting and chewing. More typically it manifests as skin lesions affecting the head, face, ears and inner thigh. These include noninflammatory alopecia, miliary dermatitis and granulomatous ulcerated skin from licking and scratching, particularly of the face and neck.
TOXIC ●
Thallium poisoning (p 1124)
Thallium-containing rodenticide toxicity results in hyperkeratosis and scaling of the footpads, as well as similar lesions elsewhere on the body.
TRAUMA ●
Shredded nail tips or avulsed nails (trauma)*** (p 1111)
Shredded nail tips or avulsed nails are typically evident in cats involved in road accidents. ●
Declawing complications (p 1120)
Deformed claws, keratinaceous foreign bodies at the ends of the digits or draining tracts may result from imperfectly completed declawing procedures. ●
Arteriovenous fistulae (p 1124)
An arteriovenous fistula is a very rare condition resulting in local edema and distinct, tortuous, pulsating blood vessels near the area.
INTRODUCTION
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Disorders of the claws and paronychia, which usually result from trauma, bacterial paronychia or neoplasia.
MECHANISM? Foot problems are less commonly seen in cats as a presenting complaint than in dogs. The feet of cats can be affected, along with other areas of the body, in numerous feline dermatoses and systemic diseases. Lesions confined primarily to the paw or pads are rarely seen. Three categories of lesions are seen: ● Scaling, crusting and pruritic lesions, which usually result from immune-mediated and allergic diseases or infectious causes such as viral, fungal and parasitic. ● Nodules, draining tracts, ulcers and abscesses, which usually result from the more unusual bacterial and fungal infections or neoplasia.
WHERE? Disorders of the feet including paws, pads, claws and ungual folds. Careful history taking and a thorough physical examination are very important in establishing a list of differential diagnoses and for selection of appropriate laboratory tests. For many of the diseases, definitive diagnosis is by histological evaluation of biopsy specimens.
WHAT? The most common causes of foot problems are infectious agents, especially bacterial and fungal, and trauma.
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Less common causes are tumors, immune-mediated diseases and endocrinopathies. ●
DISEASES CAUSING PAD OR PAW PROBLEMS SHREDDED NAIL TIPS OR AVULSED NAILS (TRAUMA)*** Classical signs ● ●
Broken or torn claws. Feathered ends to claws.
Clinical signs Broken or torn claws. Feathered ends to claws are classically seen in cats involved in a road accident, and result from dragging of the claws on the rough road surface. ● If the history of an injured cat is unknown, then feathered claw tips can be a clue to road trauma.
Diagnosis Diagnosis is based on history and physical examination.
INFECTIOUS PODODERMATITIS*** Classical signs ● ● ●
Paronychia involving one or more claws. Ulcerated nodules or fistulated areas. Non-pruritic, erythematous, scaling, alopecic lesions.
medius, Escherichia coli, Pseudomonas sp., Proteus sp. or Pasteurella sp. More rarely other bacteria reported are Mycobacterium sp., Listeria monocytogenes, Dermatophilus congolensis, Nocardia asteroides.
Fungal. ● Dermatophytes, primarily Microsporum canis, M. gypseum and Trichophyton mentagrophytes, can be found on the paws but would rarely be found there as the only site on the body. ● Rare cases of opportunistic saprophytic fungal infections have been reported including: – Pheohyphomycosis caused by Exophiala jeanselmei, Moniliella sauveolens, Cladosporium sp., Stemphyllium sp. and Scolecobasidium humicola. – Paecilomyces fumosoroseus and Sporothrix schenckii. ● Yeast infections with Cryptococcus neoformans, Rhodotorula mucilaginosa and Malassezia pachydermatis usually also involve other areas of the body. Viral. ● Pox virus causes foot lesions and is covered separately (see page 1113). ● Occasionally Calici virus may cause footpad ulceration, in addition to the more common clinical signs in other organs. Parasitic. ● Demodicosis is reported to be a rare cause of claw disease. ● An opportunistic infection with Leishmania braziliensis has been reported causing a large vegetative lesion in the interdigital area.
Clinical signs Pathogenesis Common cause of foot problems in cats and is often secondary to factors such as trauma or immune suppression (FeLV, FIV, systemic disease). Infectious agents can be bacterial, fungal or viral. Bacterial. ● Various opportunistic bacteria have been reported, most commonly Staphylococcus inter-
Bacterial. ● Paronychia involving one or more claws, and more rarely pyoderma or fistulated interdigital abscesses are usually caused by the more common opportunistic bacterial infections such as S. intermedius. ● Single or multiple ulcerated nodules, or draining fistulated areas are usually associated with the rare opportunistic bacterial (including Nocardia, Listeria monocytogenes Dermatophilus congolensis) and fungal infections.
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Fungal. ● A variety of saprophytic fungi produce draining tracts, ulcerated nodules and chronic non-healing wounds. Pheomycotic lesions are very darkly (black) pigmented. ● Kerion (nodular furunculosis) formation and onychomycosis (fungal claw infection) are rare. ● Malassezia pachydermatitis is a yeast which is a secondary infectious agent, causing brown staining at the base of the nails only, or a more generalized scaly erythematous dermatitis. Rarely it causes paronychia involving one or more claws. ● Infection by dermatophytes causes hair loss and rarely infection of the nails (onychomycosis). Other areas of the body are usually also involved with irregular or circular alopecic patches, with or without scale, that are non-pruritic and may be erythematous. Viral. ● Pox virus produces multiple papules, vesicles, plaques or crusts and ulcers, which may occur on the face, ears, limbs and paws. Paronychia and sloughing of footpads may occur. ● Calici virus infection may produce footpad ulceration in association with oral ulceration, usually without the more classical respiratory signs of sneezing and nasal discharge. Parasitic. ● Erythematous, alopecic lesions may occur with Demodex cati infections, or pruritic crusting lesions with Notoedres cati. Usually there are lesions on other parts of the body.
Diagnosis Wood’s lamp examination or direct examination of hair and scales mounted in paraffin oil or KOH may detect dermatophytes. Cytological examination of smears of the exudate from moist lesions, stained with Diff-Qik may reveal the primary organism present including Malassezia, Cryptococcus or bacteria. Culture exudate to identify the organism, and obtain sensitivity for antibiotic treatment if bacterial. Biopsy nodular or fistulous areas for histopathology, and culture tissue to identify the rarer opportunistic infections.
Serology to detect cryptococcal antibody is usually positive in cats with cryptococcosis. Hair pluck/skin scrape to detect Demodex.
Differential diagnosis Symmetrical bacterial paronychia can appear similar to immune-mediated disease such as pemphigus foliaceus. Nodules and ulcerated areas can appear similar to neoplastic lesions.
Treatment Bacterial infections. ● Use appropriate antibiotics selected based on culture and sensitivity. ● Treatment for several weeks may be necessary for deep infections. ● If lesion recurs, check immune status (FeLV, FIV, systemic disease). Fungal infections. ● Griseofulvin (50–100 mg/kg PO q 24 h, preferably with a fatty meal) is effective only for dermatophytes. Beware of adverse drug reactions including teratogenicity, gastrointestinal upsets and bone marrow suppression. ● Ketoconazole (5–10 mg/kg PO q 24 h) has been effective for most fungal and yeast infections but has more side effects than itraconazole. Adverse reactions include anorexia, fever, depression, vomiting, diarrhea and neurologic abnormalities. Lower doses or alternate day therapy may be necessary if reactions occur. ● Itraconazole (5–10 mg/kg PO q 24 h) may work better than ketoconazole, and has fewer side effects, but is more expensive. Parasitic infections. Demodex. ● Feline demodicosis has responded to simple treatments such as three dips of malathion or limesulfur at weekly intervals. ● Ivermectin is very effective against mites, although its use in cats is off-label. For demodectic mange the dose rate is 0.6 mg/kg daily orally continued
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for up to 30 days after negative skin scrapings. Stopping too early results in relapses. Similarly Doramectin at 0.6 mg/kg sc weekly can be used.
Leishmania. ● Successful treatment in cats has not been reported.
Prognosis Prognosis varies depending on the type of infection and the underlying cause. The recurrence rate is high for bacterial paronychia if there is an underlying immune deficiency. The prognosis is more guarded for the rarer opportunistic bacterial and fungal infections. Cures are reported with the use of the imidazole drugs (ketoconazole and itraconazole).
HYPERTHYROIDISM** Classical signs ● ● ●
Weight loss with polyphagia. Unkempt hair coat. Nervous, hyperactive.
See main reference on page 304 for details (The Cat With Weight Loss and a Good Appetitie).
Clinical signs Most commonly there is weight loss despite a ravenous appetite. More rarely is appetite depressed. Other signs may include tachycardia, polydipsia/ polyuria, vomiting or diarrhea, and a heart murmur. A palpable thyroid nodule in the neck is present in the majority of cats. Restlessness and hyperexcitability are often evident.
HYPERPIGMENTATION (LENTIGO SIMPLEX)** Classical signs ● ●
Black asymptomatic spots that gradually enlarge and become more numerous. Occur in cats with orange coat color.
An unkempt haircoat and overgrown claws are typical. ● The overlong claws catch in floor coverings or click on bare floors as the cat walks. Usually occurs in cats older than 8 years of age.
Diagnosis A tentative diagnosis is based on history and physical examination.
Clinical signs Hyperpigmented areas (“freckles”) in orange (ginger) cats are termed lentigo simplex. Freckles usually appear before 1 year of age and increase in number with age. There are multiple hypermelanotic macular lesions on the nose, lips, eyelids and footpads. Lesions are asymptomatic and do not develop into melanomas.
Increased total thyroxine (T4) levels confirm the diagnosis. Cats with a high normal T4 concentration and signs consistent with hyperthyroidism should either be retested several weeks later, or free T4 concentration be measured by equilibrium dialysis, or a T3 suppression test performed. Concurrent disease can decrease a high T4 into the normal range.
FELINE POX VIRUS INFECTION** Classical signs ●
Diagnosis Diagnosis is based on the history of asymptomatic black spots developing in the poorly haired areas of cats with a ginger coat color.
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Multiple nodules, papules, crusts, and ulcerative plaques. Commonly on the face, limbs and paws. Pruritis, pain, fever, conjunctivitis and dyspnea may be present.
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Pathogenesis
Transmission
Infection is caused by a virus from the orthopoxvirus genus. The origin of the virus is unclear. It was attributed to the cow-pox virus, but now it is thought there could be a feline pox virus.
The natural reservoir for infection is not known, but is thought to be small wild animals and the cat is infected whilst hunting them.
Reported infections are from England and Europe.
Clinical signs Skin lesions occur on the face, ears, limbs and paws with multiple papules, vesicles, plaques or crusts and ulcers. On the feet there can be paronychia and sloughing of the footpads.
Transmission of cow pox virus from infected milk has also been blamed. The pox virus can be transmitted to in-contact cats, dogs and humans; immunocompromised individuals are more at risk. Warn in-contact people of the zoonotic potential. The virus is killed by most disinfectants, particularly chlorine-based ones.
Prevention Diagnosis Biopsy and histologic examination of the crust or affected skin demonstrates eosinophilic intracytoplasmic inclusion bodies within keratinocytes. Specialist tests that may be available also include a serologic test for virus-neutralizing antibodies, electron microscopy of crusts or affected skin to detect the virus, and virus isolation. Virus isolation is currently the only method for making a precise diagnosis.
Prevent the cat from hunting or contact with an infected cat.
INSECT BITE HYPERSENSITIVITY** Classical signs ● ●
Erythematous, crusted, pruritic lesions. Symmetric lesions on ear tips, face, nose and footpads.
Differential diagnosis Bacterial and fungal infections, eosinophilic granuloma and neoplasia may all cause similar lesions but can be differentiated on biopsy and histological examination.
Treatment Treatment is not thought to affect the outcome of the disease, and is not regarded as necessary as most cats recover spontaneously within 1–2 months.
Pathogenesis Hypersensitivity resulting in skin lesions is associated with flying and biting insects. It is most often seen in cats that go outdoors when mosquitoes or midges (Lasiohelia townsvillensis) are present.
Clinical signs
Glucocorticoids are contraindicated.
Thinly haired areas are most commonly affected, especially the bridge of the nose, ear tips and the junction of haired skin and the footpad (“ears, nose and toes syndrome”).
Prognosis
Lesions have a symmetrical pattern, and begin with erythematous papules to plaques.
Prognosis is good as cats recover spontaneously, however, there may be permanent scarring.
Lesions are pruritic, and the cat traumatizes itself, so that the affected areas become ulcerated and crusted.
Secondary bacterial infection should be treated with antibiotics.
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Chronic lesions develop nodules, pigment changes (dark or pale patches), and alopecia.
Prognosis and prevention
Footpads may be affected with swelling, scales or crusts, hyperkeratosis, fissures and pigment changes.
Good control of the problem is possible if the cat can be kept away from biting insects, or will tolerate insect repellent.
Diagnosis
However, lesions may increase with severity over the years if exposure cannot be controlled.
Seasonal occurrence is evident coinciding with mosquito or midge season in cats allowed outdoors.
PLASMA CELL PODODERMATITIS*
Tentative diagnosis can be confirmed by keeping the cat indoors or hospitalized for 5 days and demonstrating great improvement of lesions.
Classical signs
Biopsy and obtain small specimens (4-mm biopsy punch) carefully, as the ears and nose bleed easily and readily show scars. Histopathological changes are similar to those of cats with atopy, food and flea bite hypersensitivity.
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Differential diagnosis Food allergy commonly results in pruritis of the face, head, pinnae and neck, in contrast to just the nose and/or ears affected with insect hypersensitivity. Lesions are usually asymmetrical and very excoriated. Non-seasonal occurrence, and does not respond to the indoor confinement trial, but responds to an elimination dietary trial. Autoimmune diseases such as pemphigus foliaceus/ erythematosus and discoid lupus erythematosus typically also have a symmetric pattern, but usually there is extensive crusting and exudation of head and body. Depression and anorexia are often present. Pruritis is variable.
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Swollen, very soft footpads, generally nonpainful. Normal pad symmetry.
Pathogenesis Plasma cell pododermatitis is a rare skin disease affecting the footpads. The cause is unknown, but is thought to be immunemediated or allergic. One study found 50% of cases to be feline immunodeficiency virus-positive.
Clinical signs Typically, the footpads are swollen, very soft and fluctuant (mushy). Usually the larger metacarpal and metatarsal pads are the ones affected. Normal pad symmetry is not disturbed by the swelling, but the stretching of the skin over the swollen pad results in a white, silvery, cross-hatched appearance. Lesions involve one or more feet.
Treatment Keep the cat indoors at the times of greatest insect activity, usually early morning and dusk. Topical insect repellents applied to the affected area. Try a variety, as not many are well tolerated by cats; ointments or creams are best tolerated.
Normally, the lesions are non-painful and the cat is not lame, although cases of cats limping on the affected feet have been reported. The pad may become ulcerated, and drain hemorrhagic fluid. Some cats also have plasma cell stomatitis, immunemediated glomerulonephritis or renal amyloidosis.
Petroleum jelly smeared on the ear tips and nose has also been used successfully.
Diagnosis
Oral prednisolone (0.5–2 mg/kg on alternate days) or injectable glucocorticoids (repositol methyl prednisolone acetate, 20–40 mg/cat subcutaneously).
Fine-needle aspirate of the lesion contains large numbers of uniform plasma cells with a few neutrophils and lymphocytes.
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Deep wedge biopsy from a footpad near the pad margin is diagnostic. A punch biopsy may not go deep enough to be diagnostic. ● If a number of pads are affected choose a more mildly affected one to biopsy as a severely affected one may not heal well.
Differential diagnosis Undifferentiated sarcoma may appear very similar and needs a biopsy to differentiate.
Pruritis is present but may not be obvious to the owner. ● Over-grooming results in non-inflammatory alopecia (“fur mowing”). Foot or claw chewing may initially be the only presenting clinical sign. ● The cat drags the claws through the teeth with loud clicking noises, which brings the problem to the attention of the owner. ● One or more ulcerated areas of the paws (digits, periungual areas or interdigital spaces) may be present. ● Histologically these lesions are typical of eosinophilic granuloma complex.
Treatment This is not necessary if the cat is asymptomatic, as the disease may spontaneously regress. Immunosuppressive doses of prednisolone (up to 4 mg/kg/day) have been recommended, but may not be effective. Chrysotherapy (aurothioglucose; Solganol; 1–2 mg/kg IM weekly) may be effective. Surgical excision of the footpad. A new footpad grows back. Reported to be the best therapy at present.
Prognosis Prognosis is guarded as the recurrence rate is high, usually within 4–6 months.
ATOPY AND ADVERSE FOOD REACTION* Classical signs ● ●
Pruritis, which is manifested as scratching, licking or chewing. Skin lesions varying in severity from alopecia to miliary dermatitis to ulcerated plaques or granulomas.
Diagnosis Rule out other causes of claw problems, especially infectious pododermatitis and neoplasia. Control external parasites. A good choice is fipronil as this controls fleas, and anecdotally mites (Cheyletiella, Sarcoptes, Otodectes and Notoedres) and provides partial control of ticks. Try a dietary trial using a food source that the cat has not been exposed to before. It may take ingenuity to find a new food that the cat is willing to eat. Duck, venison or rabbit (2/3 cup) with cooked rice or pasta (1/3 cup) are often tolerated. A trial period of a minimum of 9 weeks has been advocated for cats and up to 16 weeks preferably. Re-challenge the cat with the old diet to confirm the diagnosis, although owners may be unwilling to risk signs recurring. Intradermal skin testing to test for atopy. This is technically more difficult in cats than dogs, as reactions are less intense and more transient.
PRIMARY AND SECONDARY NEOPLASIA* Classical signs ● ●
Clinical signs Atopy and adverse food reactions result in various other dermatological manifestations such as ulcerated plaques, miliary dermatitis, symmetrical alopecia and pruritis of the face and neck.
Swollen, painful digit(s) and/or paronychia. Ulcerative destructive lesion of the paw and digits.
Pathogenesis Neoplasia involving the foot is rare in cats and is usually seen in older cats. The neoplasia may be primary
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or secondary. Secondary neoplasia results from metastasis of primary neoplasia in other organs. Squamous cell carcinoma. ● Rare primary tumor arising from the nail bed epithelium. ● Appears to be more aggressive than squamous cell carcinomas in other parts of the body. ● On clinical examination it may be mistaken for paronychia or pyoderma. Metastatic digital (ungual) carcinoma. ● Usually presents as lameness associated with multicentric digital carcinoma. ● Seen in aged cats (average age 13 years) with asymptomatic bronchogenic carcinoma or squamous cell carcinoma of the lung. ● Lesions can involve a number of digits and more than one paw. Typically there is swelling of the digit, ulceration of the skin or purulent discharge, and either fixed exsheathment, deviation or loss of the nail. Fibrosarcoma. ● Seen in older cats and is not associated with feline sarcoma virus. ● Lesions are usually solitary and can involve the digits. ● The area is alopecic, ulcerated and the tumor has rapid infiltrative growth. Undifferentiated sarcoma. ● Seen in older cats and involves the footpads of one or more feet. ● Affected pads are soft, mushy, painful and maybe ulcerated. Malignant fibrous histiocytoma. ● Seen in older cats. ● The lesions are solitary, firm, poorly circumscribed, variable in size and shape and locally invasive. ● Legs, especially the paw, and shoulders are the most common sites.
Bacterial or fungal infections, especially the rarer opportunistic ones, can look very similar. Biopsy for histopathology and culture will distinguish between these.
Treatment Radical surgical excision is the treatment of choice for tumors without evidence of metastasis. Mean survival for metastatic digital carcinoma was 67 days.
PEMPHIGUS* Classical signs ● ● ●
Crust, scales, alopecia in a symmetrical pattern. Areas usually involved are face, ears, trunk, feet and mucocutaneous junctions. Occasionally have only foot lesions.
Pathogenesis Pemphigus is an immune-mediated disease, with auto-antibodies directed against intercellular cement in the epidermis causing loss of cohesion between keratinocytes and resulting in the formation of bullae. ● Bullae are very transient in cat skin due to the thin epidermis, and may not be observed. What initiates the auto-antibodies is unknown, but drugs and chronic skin disease have been implicated in some cases. Different types of autoimmune dermatitis may involve cats’ paws but the most common is Pemphigus foliaceus.
Clinical signs Diagnosis Biopsy of representative areas and histopathology.
Differential diagnosis Plasma cell pododermatitis also has swollen mushy pads, which may be ulcerated.
Erythema, oozing, crusts, scales and alopecia occur with a symmetrical pattern on the face, ears, trunk, feet and mucocutaneous junctions. Lesions commonly involve the feet and footpads, causing hyperkeratosis and ulceration. Some cats are presented with only footpad lesions and sometimes lameness.
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Paronychia and involvement of the nipples are commonly seen in cats.
Diagnosis
Prognosis Prognosis is guarded, because the inciting cause is usually unknown, and the side effects of the therapy are often severe.
Direct smears from intact vesicles or pustules may show numerous acantholytic keratinocytes; these are strongly suggestive of pemphigus. Biopsy of primary lesions or at the periphery of the most recent lesions shows subcorneal pustules consisting of acantholytic keratinocytes and neutrophils. Direct immunofluorescence of biopsies shows diffuse intercellular fluorescence.
VARIATION IN NUMBER OF DIGITS* Classical signs ● ●
Abnormal number of toes (six most common). Agenesis or fusion of digits.
Differential diagnosis Systemic lupus erythematosus is rare and usually also has systemic signs. Insect hypersensitivity is common, but lesions are usually confined to the bridge of the nose, tips of the ears, and occasionally footpads. Seasonal occurrence and history of biting insects being observed around the cat helps differentiate this from pemphigus.
Treatment Therapy is often difficult as side effects from the drugs are common. High doses of glucocorticoids (4–8 mg/kg daily) will induce remission in most cases (about 2 weeks). Once in remission, reduce to alternate day therapy and to the minimum dose which maintains remission. Chlorambucil (0.1–0.2 mg/kg every 24–48 hours) can be added if glucocorticoids are insufficiently effective. Chrysotherapy (gold salts; aurothioglucose: Solganal; Schering) has been useful in cats when other treatments have failed. Begin with 1 mg/kg IM weekly until remission, which may take up to 12 weeks to occur. If no response is evident after 12 weeks of therapy, increase dose to 1.5–2 mg/kg. Once the cat responds, give the dose every 2 weeks and then monthly for several months. Alternatively the dose can be started at 0.25 mg/kg IM for the first week, 0.5 mg/kg the second week, then 1 mg/kg weekly until remission and then a gradually decreasing dosage.
Clinical signs Variation in the normal number of digits is present from birth. Ectrodactyly is agenesis of all or part of a digit and is an inherited defect involving the fore-paws. Polydactyly refers to extra toes. ● The mode of inheritance is dominant. ● There is considerable variation from animal to animal with the number of extra toes and how perfectly formed they are. ● Usually there are six toes on each front foot, but sometimes there can be seven toes on the front feet and six on the hind feet. The hind feet are not affected unless the front feet are involved. ● The incidence varies with it being common in some countries and not seen in others. Syndactyly refers to fusion of the digits. It is also called “split-foot” or “lobster-claw”. ● Typically it manifests as a central cleft of either one or both front feet. However, there may be fusion of the bones of the foot to produce double claws. ● The evidence is for dominant heredity, possibly with variable expression, as the number of affected animals is less than expected, with some genetically affected animals appearing normal. The right side tends to be more severely affected than the left.
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IRRITANT CONTACT DERMATITIS OR CHEMICAL BURNS* Classical signs ● ● ●
Variable erythema, ulceration, necrosis of the contact areas. Hyperkeratosis and scaling. Salivation and saliva staining around the mouth and paws with chemical burns.
Pathogenesis Irritant contact dermatitis or chemical burns are commonly caused by chemicals used in the environment such as herbicides, garden fertilizers, fuel oil and other common household or cattery cleaning products and disinfectants including chlorine bleach (sodium hyperchlorite), strong alkalis, strong acids, pine oils, phenolic compounds and quaternary ammonium compounds. Chemical burns with ulceration may occur if the product is incorrectly diluted. ● Typically this occurs if the product is applied undiluted and then water is used to dilute and wash the chemical away. Highly concentrated product may remain in less accessible areas, causing chemical burns to the feet and mouth. ● Signs develop when the cat inadvertently walks on them. Most common in cats living outdoors.
Clinical signs Typically, there is erythema and ulceration of the footpads, interdigital spaces and around the nails. Usually more than one paw is affected.
Diagnosis Diagnosis is based on history and physical examination.
Treatment Bathe to remove traces of offending chemical. Corticosteroids (prednisolone, 0.5–1 mg/kg PO q 24 h) to reduce inflammation. Non-steroidal antiinflammatory drugs can be given for pain relief and to reduce inflammation. Ketoprofen is registered for use in cats (2 mg/kg SC or PO initially then 1 mg/kg PO daily). Meloxicam (0.2 mg/kg SC or PO initially then 0.025 mg/kg PO 2–3 times/week. Antibiotics, if there is secondary infection. Protective dressings may be necessary if ulceration is severe to promote healing.
BURNS (THERMAL)* Classical signs ● ● ●
Initially the skin may be dry and hard. Necrotic skin sloughs leaving large raw areas. Purulent discharge when secondarily infected.
Pathogenesis Burns occur when cats walk or jump onto hot surfaces such as barbecues or stove hot plates, usually with the intent of stealing food. More generalized burns occur in cats trapped in house fires.
Pain and pruritis are sometimes evident. Oral ulcers and salivation are often present, and result from the cat licking its feet. Regurgitation may result from chemical esophagitis. Less toxic chemicals or concentrations may cause erythema, and excessive licking of the feet rather than ulceration.
Clinical signs Signs depend on the severity of the burn, and include superficial to deep ulceration and sloughing of the burnt area. Initially the skin may be dry and hard. Necrotic skin sloughs leaving large raw areas.
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Purulent discharge occurs when the burnt area becomes secondarily infected.
Treatment Silver sulfadiazine cream or aloe vera gel applied under a non-adherent dressing are excellent topical treatments for burns.
Clinical signs Frostbite typically affects the tips of the ears and the digits, areas that are not well insulated. Whilst frozen, the skin appears pale and cool to touch, and has decreased sensation. After thawing, there may be mild erythema, edema and pain.
Burn healing is slow, taking weeks to months of treatment.
In severe cases, the skin becomes necrotic and sloughs.
Very extensive or deep burns may heal with scarring that interferes with function, necessitating reconstructive surgical procedures.
Treatment
DECLAWING COMPLICATIONS Classical signs ● ●
Claw deformity or keratinaceous growths at the end of the digits. Swollen ends of digits and draining tracts.
Clinical signs Regrowth of claws may result from persistent germinative epithelium after incomplete removal during declawing.
Rapidly thaw frozen area by the gentle application of warm (42–44˚C) water. Handle tissues gently to prevent further damage and pain. Aloe vera gel applied topically helps to prevent vasoconstriction and tissue hypoxia. Any resulting necrotic areas may need surgical debriding. Antibiotics may be needed to control secondary infection, in cases where there is extensive tissue damage.
Regrowth can vary from deformed claws to keratinaceous foreign bodies at the ends of the digits.
FOREIGN BODIES
Swollen ends of digits and draining tracts may develop.
Classical signs ●
Nodules, abscess and draining tracts.
Diagnosis A history of a declawing procedure having been performed. Excisional biopsy of deformed ends of the digits is diagnostic and curative.
FROSTBITE
Clinical signs Objects such as plant awns, thorns can become embedded in the interdigital space. This is much rarer in cats than in dogs. Nodules, abscesses and draining tracts result.
Classical signs ● ● ●
Frozen skin is pale and cool to the touch. Mild erythema, edema and pain after thawing. Necrosis and sloughing in severe cases.
Treatment Surgical debridement and removal of foreign body. Use antibiotics if secondary infection develops.
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SYSTEMIC LUPUS ERYTHEMATOSUS Classical signs ● ●
Multi-systemic disease including the skin. Generaliszd or localized erythematous, scaly or crusted skin lesions.
Clinical signs Dermatological signs occur in 20–30% of cases. ● Typically, there are generalized or localized scaly or crusted lesions on the face, ears and eyelids. Alternatively, ulcerative lesions may be present on the face, trunk and feet. Periocular leukotrichia may be evident. ● Paronychia and oily seborrhea may occur. Systemic signs include intermittent pyrexia, anorexia, depression and weight loss. Involvement of other organs may result in immunemediated anemia, thrombocytopenia, glomerulonephritis and polyarthritis.
Diagnosis Definitive diagnosis is very challenging, as the disease is so variable in its clinical presentation. Skin biopsies show hydropic interface dermatitis.
Often there is seborrhea sicca and a dry, lusterless hair coat, which is easily epilated, and has poor regrowth after clipping. The skin may be myxoedematous and thickened. Other signs of hypothyroidism may be present including lethargy, inappetence, obesity, hypothermia and bradycardia. Most commonly occurs after bilateral thyroidectomy for hyperthyroidism. Spontaneous hypothyroidism is very rare.
Diagnosis If available, the thyroid stimulation test shows minimal to no stimulation. Free T4 or free T4 by equilibrium dialysis are below the normal values for the laboratory. Response to trial therapy with thyroxine (0.05–0.1 mg once daily) for 4 weeks results in improved clinical signs.
HYPERADRENOCORTICISM Classical signs ●
A high positive ANA titer may occur in some cats.
●
Laboratory results demonstrating multi-systemic disease suggest a tentative diagnosis of SLE.
●
HYPOTHYROIDISM
Pot-bellied appearance and muscle wasting. Unkempt hair coat with thin, easily torn skin. Polydypsia/polyuria and often associated diabetes mellitus (80% of cases).
See main reference on page 251 for details (The Cat With Polyuria and Polydipsia).
Classical signs ● ●
Lethargy, inappetence, obesity. Seborrhea sicca and a dry, lusterless hair coat, easily epilated with poor regrowth.
Clinical signs Hypothyroidism may result in erythematous, scaling and papular lesions, which affect the forehead, abdomen, tail and footpads.
Clinical signs Bilaterally symmetrical alopecia involving the face, flanks and limbs. The skin is often very thin and easily torn especially on the digits. Systemic signs of polydypsia, polyuria and weight loss are usually associated with diabetes mellitus.
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Diagnosis Low-dose dexamethasone test (0.1 mg/kg) or ACTH stimulation test is used for diagnosis. Imaging the adrenals by abdominal ultrasound helps differentiate pituitary from adrenal-dependent hyperadrenocorticism.
DIABETES MELLITUS Classical signs ●
Polydypsia, polyuria, polyphagia and weight loss.
See main reference on page 236 for details (The Cat With Polyuria and Polydipsia).
Vitiligo is a hereditary lack of pigment in the skin, and may have an autoimmune pathogenesis. ● Three affected Siamese cats had antimelanocyte antibodies, whereas four normal Siamese cats did not. ● There can be symmetric macular depigmentation, especially of the nose, lips, buccal mucosa and facial skin, also footpads and claws. ● Lesions are most noticeable in the dark coat colors where the normally dark footpads have pink patches. ● Onset of the condition is usually in young adulthood.
Diagnosis
Clinical signs
Diagnosis is based on the history of a young age with patches of unpigmented skin in normally darkpigmented areas.
Cutaneous xanthomatosis has been described in cats with diabetes mellitus.
In vitiligo there is no history of trauma or inflammation that could have damaged melanocytes.
This may present as whitish, waxy nodules in the paws. Typical signs include polydypsia, polyuria, polyphagia and weight loss.
CUTANEOUS HORNS Classical signs ●
Firm, horn-like protuberance on the skin.
Diagnosis A tentative diagnosis is based on a history of polydypsia and polyuria with weight loss.
Pathogenesis
A definitive diagnosis is based on demonstrating persistent hyperglycemia > 12 mmol/L (> 216 mg/dl).
The term cutaneous horn is used to describe a keratotic mass that is generally higher than it is wide, usually several millimeters in diameter and 1–2 cm high.
HYPOMELANOSIS (VITILIGO)
Cutaneous horn of the footpads in cats is a rare disorder. Affected cats have been positive for FeLV and the virus has been isolated from the horn material.
Classical signs ●
Patches of complete lack of pigment.
The viral-affected horns occur on the footpads only.
Clinical signs
Clinical signs
Loss of epidermal pigmentation (hypomelanosis) can be primary as with vitiligo, or secondary as in postinflammatory change.
Single or multiple firm horn-like formations arising from any area of skin. Footpads seem to be predisposed sites.
53 – THE CAT WITH PAW OR PAD PROBLEMS
Diagnosis Diagnosis is based on the typical clinical appearance and histopathology of dense laminated hyperkeratosis. Biopsy may be necessary to check for squamous cell carcinoma at the base. Check FeLV status.
Treatment Surgical excision is the treatment of choice. Recurrences are frequent.
CALCINOSIS CUTIS Classical signs ● ● ●
Enlarged, painful and firm pads. The pads may be ulcerated and exuding a white paste of gritty material. Signs of chronic renal disease.
See main reference on page 245 (The Cat With Polyuria and Polydipsia).
Clinical signs Calcinosis cutis is a rare complication of chronic renal disease. Affected pads are enlarged, firm and painful. A chalky white-to-pink material with feathery margins may be seen through the intact epidermis of nonulcerated lesions. Older lesions may ulcerate and extrude a chalky, white, pasty to gritty material. Other signs associated with chronic renal disease such as polyuria/polydypsia, and weight loss.
EPIDERMOLYSIS BULLOSA Classical signs ● ● ●
Uncommon congenital disorder. Avulsion of the claws with minor trauma. Erosive lesions on the hard palate.
Pathogenesis Separation of epidermal tissues from the dermis occurs after minor trauma because of defective adherence of the dermo–epidermal junction. Epidermolysis bullosa is an uncommon congenital disorder, that has been reported in a line of Siamese cats.
Clinical signs Nails are shed after minor trauma. The entire claw is avulsed, leaving the corium quick exposed. Regrown claws may be deformed. There may also be ulcers on the footpads and hard palate. The onset is noticed when kittens become ambulatory and start climbing. Lesions may have secondary bacterial infection.
Diagnosis A definitive diagnosis is based on histopathology of an amputated P3 which demonstrates dermo– epidermal separation without inflammation or basal cell injury.
Diagnosis
Differential diagnosis
A definitive diagnosis is based on biopsy of the lesion that demonstrates metastatic calcium deposition in the tissues.
Bacterial paronychia can be very similar, but the history and histopathology will differentiate.
Clinical and laboratory findings are consistent with chronic renal failure.
Immune-mediated disease affecting the claws, but generally there are severe dermatological signs elsewhere on the body.
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Treatment Curative treatment is not available, but amputation of P3 of affected digits will prevent recurrent claw loss with associated pain and infection. Secondary infection should be managed with suitable antibiotics. Avoid trauma.
ARTERIOVENOUS FISTULAE Classical signs ● ●
Localized persistent or recurrent edema. Distinct and tortuous blood vessels near the area.
THALLIUM POISONING Classical signs ● ● ● ●
Easily epilated hair. Cutaneous erythema, erosions, crusts, necrosis and alopecia. Lesions on ears, nose, abdomen. Marked redness of mucous membranes.
Pathogenesis Thallium is a cumulative rodenticide rapidly absorbed through the mucosae and skin. Its use is now banned in many countries.
Clinical signs Pathogenesis Arteriovenous fistulae are traumatically induced from penetrating wounds, blunt trauma or post-surgical complications of onychectomy.
Skin lesions are seen in association with chronic toxicity, and are characterized by chronic dermatitis. There is severe redness of mucous membranes, cutaneous erythema, erosions, crusts, necrosis and alopecia. Lesions are usually present around body orifices and on the nose, ears, abdomen and feet. The footpads become hyperkeratotic and ulcerated.
Clinical signs
Hair is easily epilated.
Arteriovenous fistulae may be associated with persistent or recurrent edema and bacterial paronychia of one paw.
Diagnosis
Pulsating blood vessels, palpable thrills and continuous machinery murmurs are present in the area of the fistula.
Diagnosis is based on a history of exposure to thallium and positive test for thallium in the urine. Skin biopsies demonstrate dermatitis consistent with thallium poisoning.
Diagnosis
Differential diagnosis
A tentative diagnosis is based on the clinical signs.
A number of diseases can have a similar crusted and ulcerated appearance, and distribution to thallium toxicosis, and skin biopsies are needed to differentiate. These include: ● Autoimmune disorders. ● Drug eruptions. ● Erythema multiforme and toxic epidermal necrolysis. ● Lymphoreticular neoplasia.
Definitive diagnosis is by demonstration of the fistula by contrast radiography.
Treatment Surgical removal of the fistula or amputation of the affected part.
53 – THE CAT WITH PAW OR PAD PROBLEMS
Treatment Prussian blue (100 mg/kg IV) given daily until urinary tests for thallium are negative has been used to treat thallium toxicosis, but is relatively ineffective when clinical signs are already present. The recommendation at present is combination treatment with charcoal for gastrointestinal trapping of thallium and potassium chloride supplementation
(1–2 g q 8–12 h) to promote renal excretion of thallium. Supportive care such as intravenous fluids and antibiotics for secondary infection.
Prognosis Prognosis is very guarded, and most cases die.
RECOMMENDED READING Bertazzolo W, Toscani L, Calcaterra S, Crippa L, Caniatti M, Bonfanti U. Clinicopathological findings in five cats with paw calcification J Feline Med Surg 2003; 5: 11–17. Dias-Pereira P; Faustino A. Feline plasma cell pododermatitis: a study of 8 cases. Vet Dermatol 2003; 14: 333–337. Foil CS. Facial, pedal, and other regional dermatoses. Vet Clin North Am Small Anim Pract 1995; 25: 923–944. Guaguere E, Hubert B, DeLabre C. Feline dermatoses. Vet Derm 1992; 3: 1–12. Scott DW, Miller WH Jr, Disorders of the claw and clawbeds in cats. Comp Cont Educ 1992; 14: 449–455. Scott DW, Miller WH Jr, Griffin CE. Muller and Kirk’s Small Animal Dermatology, 5th edn. 1995.
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KEY SIGNS ● ● ●
Erythema, scaling, crusting, and/or pruritic lesions. Nodules, draining tracts, ulcers and/or abscesses. Distortion of the nails or deformity of the foot.
MECHANISM? ●
A wide variety of diseases can have paw or pad problems as part of more generalized signs, or the lesions can be confined solely to the foot.
●
Disease of the feet includes the paw, pads, digits and nails. Interdigital spaces are seldom affected in cats. It is rare for the disease to be confined solely to the feet. Usually the feet are affected in conjunction with other areas of the skin.
WHERE?
●
WHAT? The most common problems seen in the paw are: ● Bacterial paronychia from a variety of causes. ● Immune-mediated diseases. ● Nodules or ulceration due to infections or neoplasia.
QUICK REFERENCE SUMMARY
Diseases causing paw or pad problems ANOMALY ●
Variation in number of the digits* (p 1118)
Hereditary variations in the number of digits, generally six toes, occur most commonly on the front feet. ●
Hypomelanosis (vitiligo) (p 1122)
Loss of epidermal melanin is evidenced by non-pigmented patches in otherwise pigmented areas such as the nose, lips, mouth and paw pads. continued 1107
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continued ●
Hyperpigmentation (lentigo simplex)** (p 1113)
Dark pigmented patches (“freckles”) occur in the non-haired areas of orange cats older than 1 year of age. ●
Epidermolysis bullosa (p 1123)
A hereditary claw-shedding disease seen in Siamese kittens causes the claws to shed easily with minor trauma.
METABOLIC ●
Hypothyroidism (p 1121)
Erythematous, scaling lesions of the footpads occasionally occur with hypothyroidism. Seborrhea sicca and a dry lusterless hair coat, which is easily epilated, and has poor regrowth after clipping may be evident. It is very rare in cats, and occurs most commonly after bilateral thyroidectomy. ●
Hyperthyroidism** (p 1113)
Unkempt hair coat and overgrown claws are commonly seen. Systemic signs include weight loss, polyphagia, polydypsia/polyuria and nervous/hyperactive temperament. Usually seen in cats older than 8 years. ●
Hyperadrenocorticism (p 1121)
Rare condition in cats that results in very thin and easily torn skin, especially on the digits. Other systemic signs include polyphagia, polydypsia/polyuria, abdominal enlargement and skin infections. ●
Diabetes mellitus (p 1122)
Whitish, waxy nodules in the paws are a rare complication of diabetes mellitis. Other systemic signs include polyuria/polydypsia, weight loss and polyphagia or anorexia. ●
Calcinosis cutis (p 1123)
Metastatic calcification occasionally occurs in the pads of the feet secondary to renal failure. Affected pads are enlarged, firm and painful. A chalky white-to-pink material may be visible through the intact epidermis. Pads may ulcerate and exude a chalky, white, pasty material.
MECHANICAL ●
Foreign bodies (p 1120)
Foreign bodies may result in nodules, abscesses or draining tracts in the interdigital web. Foreign bodies are much rarer in cats than dogs.
NEOPLASTIC ●
Primary and secondary neoplasia (p 1116)
Neoplasia may cause swollen painful pads or digits that become ulcerated. Various neoplasms have been recorded as having a predilection for the feet; squamous cell carcinoma, metastatic ungual carcinoma, fibrosarcoma and malignant fibrous histiocytoma have been more commonly reported. ●
Cutaneous horns (p 1122)
Cones of hard keratin growing out from the skin occasionally occur on the feet.
53 – THE CAT WITH PAW OR PAD PROBLEMS
PHYSICAL ●
Irritant contact dermatitis or chemical burns* (p 1119)
Erythema and ulceration of the footpads often occur together with salivation, mouth ulcers and anorexia. ●
Burns (thermal)* (p 1119)
Superficial to deep ulceration on the footpads occurs, depending on the severity of the burn. ●
Frostbite (p 1120)
Frostbite may result in erythema, edema, necrosis and sloughing of extremities.
INFECTIOUS (VIRAL) ●
Feline pox virus infection** (p 1113)
Multiple papules, vesicles, plaques or crusts and ulcers may occur on the face, ears, limbs and paws associated with pox virus. Paronychia and sloughing of footpads may occur. ●
Infectious pododermatitis*** (p 1111)
Viral, bacterial (most common), fungal and parasitic agents may cause pad and paw disease. Bacterial: Paronychia involving one or more claws, and more rarely pyoderma or fistulated interdigital abscesses are usually caused by the more common opportunistic bacterial infections such as S. intermedius and more rarely by the yeast M. pachydermatitis. Fungal: Single or multiple ulcerated nodules, or draining fistulated areas are usually associated with the rare opportunistic bacterial and fungal infections. Pheomycotic lesions are very darkly (black) pigmented. Nonpruritic, erythematous scaling, alopecic lesions are associated with dermatophytes and usually there are lesions elsewhere on the body as well. Kerion (nodular furunculosis) formation and onychomycosis (fungal claw infection) are rare. Malassezia causes brown staining at the base of the nails only, or a more generalized scaly erythematous dermatitis. Viral: Calici virus may produce footpad ulceration in association with oral ulceration, usually without the more classical respiratory signs of sneezing and nasal discharge. Parasitic: Erythematous, alopecic lesions may occur with Demodex cati infections, or pruritic crusting lesions with Notoedres cati. Usually there are lesions on other parts of the body.
INFLAMMATION (IMMUNE-MEDIATED) ●
Pemphigus* (p 1117)
Pemphigus foliaceus is most common. A symmetrical pattern of lesions occurs on the face, ears, trunk, feet and mucocutaneous junctions consisting of erythema, oozing, crust, scales and alopecia. Some cats may present with only foot lesions. ●
Systemic lupus erythematosus (p 1121)
SLE is a multi-systemic disease, which may involve the skin with ulcerative lesions of the feet and paronychia. ●
Plasma cell pododermatitis* (p 1115)
Plasma cell pododermatitis results in swollen and very soft (“mushy”) footpads with normal pad symmetry. Normally it is non-painful, but the pads may become ulcerated. ●
Insect bite hypersensitivity** (p 1114)
Symmetrical pattern of erythematous papules, ulcers and crusts occur on thinly haired areas, especially the bridge of the nose and/or ear tips. Sometimes the footpads are also affected. Lesions have a seasonal occurrence. continued
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continued
ALLERGY ●
Atopy and adverse food reaction* (p 1116)
Atopy or adverse food reaction may just involve the feet with nail biting and chewing. More typically it manifests as skin lesions affecting the head, face, ears and inner thigh. These include noninflammatory alopecia, miliary dermatitis and granulomatous ulcerated skin from licking and scratching, particularly of the face and neck.
TOXIC ●
Thallium poisoning (p 1124)
Thallium-containing rodenticide toxicity results in hyperkeratosis and scaling of the footpads, as well as similar lesions elsewhere on the body.
TRAUMA ●
Shredded nail tips or avulsed nails (trauma)*** (p 1111)
Shredded nail tips or avulsed nails are typically evident in cats involved in road accidents. ●
Declawing complications (p 1120)
Deformed claws, keratinaceous foreign bodies at the ends of the digits or draining tracts may result from imperfectly completed declawing procedures. ●
Arteriovenous fistulae (p 1124)
An arteriovenous fistula is a very rare condition resulting in local edema and distinct, tortuous, pulsating blood vessels near the area.
INTRODUCTION
●
Disorders of the claws and paronychia, which usually result from trauma, bacterial paronychia or neoplasia.
MECHANISM? Foot problems are less commonly seen in cats as a presenting complaint than in dogs. The feet of cats can be affected, along with other areas of the body, in numerous feline dermatoses and systemic diseases. Lesions confined primarily to the paw or pads are rarely seen. Three categories of lesions are seen: ● Scaling, crusting and pruritic lesions, which usually result from immune-mediated and allergic diseases or infectious causes such as viral, fungal and parasitic. ● Nodules, draining tracts, ulcers and abscesses, which usually result from the more unusual bacterial and fungal infections or neoplasia.
WHERE? Disorders of the feet including paws, pads, claws and ungual folds. Careful history taking and a thorough physical examination are very important in establishing a list of differential diagnoses and for selection of appropriate laboratory tests. For many of the diseases, definitive diagnosis is by histological evaluation of biopsy specimens.
WHAT? The most common causes of foot problems are infectious agents, especially bacterial and fungal, and trauma.
53 – THE CAT WITH PAW OR PAD PROBLEMS
Less common causes are tumors, immune-mediated diseases and endocrinopathies. ●
DISEASES CAUSING PAD OR PAW PROBLEMS SHREDDED NAIL TIPS OR AVULSED NAILS (TRAUMA)*** Classical signs ● ●
Broken or torn claws. Feathered ends to claws.
Clinical signs Broken or torn claws. Feathered ends to claws are classically seen in cats involved in a road accident, and result from dragging of the claws on the rough road surface. ● If the history of an injured cat is unknown, then feathered claw tips can be a clue to road trauma.
Diagnosis Diagnosis is based on history and physical examination.
INFECTIOUS PODODERMATITIS*** Classical signs ● ● ●
Paronychia involving one or more claws. Ulcerated nodules or fistulated areas. Non-pruritic, erythematous, scaling, alopecic lesions.
medius, Escherichia coli, Pseudomonas sp., Proteus sp. or Pasteurella sp. More rarely other bacteria reported are Mycobacterium sp., Listeria monocytogenes, Dermatophilus congolensis, Nocardia asteroides.
Fungal. ● Dermatophytes, primarily Microsporum canis, M. gypseum and Trichophyton mentagrophytes, can be found on the paws but would rarely be found there as the only site on the body. ● Rare cases of opportunistic saprophytic fungal infections have been reported including: – Pheohyphomycosis caused by Exophiala jeanselmei, Moniliella sauveolens, Cladosporium sp., Stemphyllium sp. and Scolecobasidium humicola. – Paecilomyces fumosoroseus and Sporothrix schenckii. ● Yeast infections with Cryptococcus neoformans, Rhodotorula mucilaginosa and Malassezia pachydermatis usually also involve other areas of the body. Viral. ● Pox virus causes foot lesions and is covered separately (see page 1113). ● Occasionally Calici virus may cause footpad ulceration, in addition to the more common clinical signs in other organs. Parasitic. ● Demodicosis is reported to be a rare cause of claw disease. ● An opportunistic infection with Leishmania braziliensis has been reported causing a large vegetative lesion in the interdigital area.
Clinical signs Pathogenesis Common cause of foot problems in cats and is often secondary to factors such as trauma or immune suppression (FeLV, FIV, systemic disease). Infectious agents can be bacterial, fungal or viral. Bacterial. ● Various opportunistic bacteria have been reported, most commonly Staphylococcus inter-
Bacterial. ● Paronychia involving one or more claws, and more rarely pyoderma or fistulated interdigital abscesses are usually caused by the more common opportunistic bacterial infections such as S. intermedius. ● Single or multiple ulcerated nodules, or draining fistulated areas are usually associated with the rare opportunistic bacterial (including Nocardia, Listeria monocytogenes Dermatophilus congolensis) and fungal infections.
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Fungal. ● A variety of saprophytic fungi produce draining tracts, ulcerated nodules and chronic non-healing wounds. Pheomycotic lesions are very darkly (black) pigmented. ● Kerion (nodular furunculosis) formation and onychomycosis (fungal claw infection) are rare. ● Malassezia pachydermatitis is a yeast which is a secondary infectious agent, causing brown staining at the base of the nails only, or a more generalized scaly erythematous dermatitis. Rarely it causes paronychia involving one or more claws. ● Infection by dermatophytes causes hair loss and rarely infection of the nails (onychomycosis). Other areas of the body are usually also involved with irregular or circular alopecic patches, with or without scale, that are non-pruritic and may be erythematous. Viral. ● Pox virus produces multiple papules, vesicles, plaques or crusts and ulcers, which may occur on the face, ears, limbs and paws. Paronychia and sloughing of footpads may occur. ● Calici virus infection may produce footpad ulceration in association with oral ulceration, usually without the more classical respiratory signs of sneezing and nasal discharge. Parasitic. ● Erythematous, alopecic lesions may occur with Demodex cati infections, or pruritic crusting lesions with Notoedres cati. Usually there are lesions on other parts of the body.
Diagnosis Wood’s lamp examination or direct examination of hair and scales mounted in paraffin oil or KOH may detect dermatophytes. Cytological examination of smears of the exudate from moist lesions, stained with Diff-Qik may reveal the primary organism present including Malassezia, Cryptococcus or bacteria. Culture exudate to identify the organism, and obtain sensitivity for antibiotic treatment if bacterial. Biopsy nodular or fistulous areas for histopathology, and culture tissue to identify the rarer opportunistic infections.
Serology to detect cryptococcal antibody is usually positive in cats with cryptococcosis. Hair pluck/skin scrape to detect Demodex.
Differential diagnosis Symmetrical bacterial paronychia can appear similar to immune-mediated disease such as pemphigus foliaceus. Nodules and ulcerated areas can appear similar to neoplastic lesions.
Treatment Bacterial infections. ● Use appropriate antibiotics selected based on culture and sensitivity. ● Treatment for several weeks may be necessary for deep infections. ● If lesion recurs, check immune status (FeLV, FIV, systemic disease). Fungal infections. ● Griseofulvin (50–100 mg/kg PO q 24 h, preferably with a fatty meal) is effective only for dermatophytes. Beware of adverse drug reactions including teratogenicity, gastrointestinal upsets and bone marrow suppression. ● Ketoconazole (5–10 mg/kg PO q 24 h) has been effective for most fungal and yeast infections but has more side effects than itraconazole. Adverse reactions include anorexia, fever, depression, vomiting, diarrhea and neurologic abnormalities. Lower doses or alternate day therapy may be necessary if reactions occur. ● Itraconazole (5–10 mg/kg PO q 24 h) may work better than ketoconazole, and has fewer side effects, but is more expensive. Parasitic infections. Demodex. ● Feline demodicosis has responded to simple treatments such as three dips of malathion or limesulfur at weekly intervals. ● Ivermectin is very effective against mites, although its use in cats is off-label. For demodectic mange the dose rate is 0.6 mg/kg daily orally continued
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●
for up to 30 days after negative skin scrapings. Stopping too early results in relapses. Similarly Doramectin at 0.6 mg/kg sc weekly can be used.
Leishmania. ● Successful treatment in cats has not been reported.
Prognosis Prognosis varies depending on the type of infection and the underlying cause. The recurrence rate is high for bacterial paronychia if there is an underlying immune deficiency. The prognosis is more guarded for the rarer opportunistic bacterial and fungal infections. Cures are reported with the use of the imidazole drugs (ketoconazole and itraconazole).
HYPERTHYROIDISM** Classical signs ● ● ●
Weight loss with polyphagia. Unkempt hair coat. Nervous, hyperactive.
See main reference on page 304 for details (The Cat With Weight Loss and a Good Appetitie).
Clinical signs Most commonly there is weight loss despite a ravenous appetite. More rarely is appetite depressed. Other signs may include tachycardia, polydipsia/ polyuria, vomiting or diarrhea, and a heart murmur. A palpable thyroid nodule in the neck is present in the majority of cats. Restlessness and hyperexcitability are often evident.
HYPERPIGMENTATION (LENTIGO SIMPLEX)** Classical signs ● ●
Black asymptomatic spots that gradually enlarge and become more numerous. Occur in cats with orange coat color.
An unkempt haircoat and overgrown claws are typical. ● The overlong claws catch in floor coverings or click on bare floors as the cat walks. Usually occurs in cats older than 8 years of age.
Diagnosis A tentative diagnosis is based on history and physical examination.
Clinical signs Hyperpigmented areas (“freckles”) in orange (ginger) cats are termed lentigo simplex. Freckles usually appear before 1 year of age and increase in number with age. There are multiple hypermelanotic macular lesions on the nose, lips, eyelids and footpads. Lesions are asymptomatic and do not develop into melanomas.
Increased total thyroxine (T4) levels confirm the diagnosis. Cats with a high normal T4 concentration and signs consistent with hyperthyroidism should either be retested several weeks later, or free T4 concentration be measured by equilibrium dialysis, or a T3 suppression test performed. Concurrent disease can decrease a high T4 into the normal range.
FELINE POX VIRUS INFECTION** Classical signs ●
Diagnosis Diagnosis is based on the history of asymptomatic black spots developing in the poorly haired areas of cats with a ginger coat color.
● ●
Multiple nodules, papules, crusts, and ulcerative plaques. Commonly on the face, limbs and paws. Pruritis, pain, fever, conjunctivitis and dyspnea may be present.
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Pathogenesis
Transmission
Infection is caused by a virus from the orthopoxvirus genus. The origin of the virus is unclear. It was attributed to the cow-pox virus, but now it is thought there could be a feline pox virus.
The natural reservoir for infection is not known, but is thought to be small wild animals and the cat is infected whilst hunting them.
Reported infections are from England and Europe.
Clinical signs Skin lesions occur on the face, ears, limbs and paws with multiple papules, vesicles, plaques or crusts and ulcers. On the feet there can be paronychia and sloughing of the footpads.
Transmission of cow pox virus from infected milk has also been blamed. The pox virus can be transmitted to in-contact cats, dogs and humans; immunocompromised individuals are more at risk. Warn in-contact people of the zoonotic potential. The virus is killed by most disinfectants, particularly chlorine-based ones.
Prevention Diagnosis Biopsy and histologic examination of the crust or affected skin demonstrates eosinophilic intracytoplasmic inclusion bodies within keratinocytes. Specialist tests that may be available also include a serologic test for virus-neutralizing antibodies, electron microscopy of crusts or affected skin to detect the virus, and virus isolation. Virus isolation is currently the only method for making a precise diagnosis.
Prevent the cat from hunting or contact with an infected cat.
INSECT BITE HYPERSENSITIVITY** Classical signs ● ●
Erythematous, crusted, pruritic lesions. Symmetric lesions on ear tips, face, nose and footpads.
Differential diagnosis Bacterial and fungal infections, eosinophilic granuloma and neoplasia may all cause similar lesions but can be differentiated on biopsy and histological examination.
Treatment Treatment is not thought to affect the outcome of the disease, and is not regarded as necessary as most cats recover spontaneously within 1–2 months.
Pathogenesis Hypersensitivity resulting in skin lesions is associated with flying and biting insects. It is most often seen in cats that go outdoors when mosquitoes or midges (Lasiohelia townsvillensis) are present.
Clinical signs
Glucocorticoids are contraindicated.
Thinly haired areas are most commonly affected, especially the bridge of the nose, ear tips and the junction of haired skin and the footpad (“ears, nose and toes syndrome”).
Prognosis
Lesions have a symmetrical pattern, and begin with erythematous papules to plaques.
Prognosis is good as cats recover spontaneously, however, there may be permanent scarring.
Lesions are pruritic, and the cat traumatizes itself, so that the affected areas become ulcerated and crusted.
Secondary bacterial infection should be treated with antibiotics.
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Chronic lesions develop nodules, pigment changes (dark or pale patches), and alopecia.
Prognosis and prevention
Footpads may be affected with swelling, scales or crusts, hyperkeratosis, fissures and pigment changes.
Good control of the problem is possible if the cat can be kept away from biting insects, or will tolerate insect repellent.
Diagnosis
However, lesions may increase with severity over the years if exposure cannot be controlled.
Seasonal occurrence is evident coinciding with mosquito or midge season in cats allowed outdoors.
PLASMA CELL PODODERMATITIS*
Tentative diagnosis can be confirmed by keeping the cat indoors or hospitalized for 5 days and demonstrating great improvement of lesions.
Classical signs
Biopsy and obtain small specimens (4-mm biopsy punch) carefully, as the ears and nose bleed easily and readily show scars. Histopathological changes are similar to those of cats with atopy, food and flea bite hypersensitivity.
●
Differential diagnosis Food allergy commonly results in pruritis of the face, head, pinnae and neck, in contrast to just the nose and/or ears affected with insect hypersensitivity. Lesions are usually asymmetrical and very excoriated. Non-seasonal occurrence, and does not respond to the indoor confinement trial, but responds to an elimination dietary trial. Autoimmune diseases such as pemphigus foliaceus/ erythematosus and discoid lupus erythematosus typically also have a symmetric pattern, but usually there is extensive crusting and exudation of head and body. Depression and anorexia are often present. Pruritis is variable.
●
Swollen, very soft footpads, generally nonpainful. Normal pad symmetry.
Pathogenesis Plasma cell pododermatitis is a rare skin disease affecting the footpads. The cause is unknown, but is thought to be immunemediated or allergic. One study found 50% of cases to be feline immunodeficiency virus-positive.
Clinical signs Typically, the footpads are swollen, very soft and fluctuant (mushy). Usually the larger metacarpal and metatarsal pads are the ones affected. Normal pad symmetry is not disturbed by the swelling, but the stretching of the skin over the swollen pad results in a white, silvery, cross-hatched appearance. Lesions involve one or more feet.
Treatment Keep the cat indoors at the times of greatest insect activity, usually early morning and dusk. Topical insect repellents applied to the affected area. Try a variety, as not many are well tolerated by cats; ointments or creams are best tolerated.
Normally, the lesions are non-painful and the cat is not lame, although cases of cats limping on the affected feet have been reported. The pad may become ulcerated, and drain hemorrhagic fluid. Some cats also have plasma cell stomatitis, immunemediated glomerulonephritis or renal amyloidosis.
Petroleum jelly smeared on the ear tips and nose has also been used successfully.
Diagnosis
Oral prednisolone (0.5–2 mg/kg on alternate days) or injectable glucocorticoids (repositol methyl prednisolone acetate, 20–40 mg/cat subcutaneously).
Fine-needle aspirate of the lesion contains large numbers of uniform plasma cells with a few neutrophils and lymphocytes.
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Deep wedge biopsy from a footpad near the pad margin is diagnostic. A punch biopsy may not go deep enough to be diagnostic. ● If a number of pads are affected choose a more mildly affected one to biopsy as a severely affected one may not heal well.
Differential diagnosis Undifferentiated sarcoma may appear very similar and needs a biopsy to differentiate.
Pruritis is present but may not be obvious to the owner. ● Over-grooming results in non-inflammatory alopecia (“fur mowing”). Foot or claw chewing may initially be the only presenting clinical sign. ● The cat drags the claws through the teeth with loud clicking noises, which brings the problem to the attention of the owner. ● One or more ulcerated areas of the paws (digits, periungual areas or interdigital spaces) may be present. ● Histologically these lesions are typical of eosinophilic granuloma complex.
Treatment This is not necessary if the cat is asymptomatic, as the disease may spontaneously regress. Immunosuppressive doses of prednisolone (up to 4 mg/kg/day) have been recommended, but may not be effective. Chrysotherapy (aurothioglucose; Solganol; 1–2 mg/kg IM weekly) may be effective. Surgical excision of the footpad. A new footpad grows back. Reported to be the best therapy at present.
Prognosis Prognosis is guarded as the recurrence rate is high, usually within 4–6 months.
ATOPY AND ADVERSE FOOD REACTION* Classical signs ● ●
Pruritis, which is manifested as scratching, licking or chewing. Skin lesions varying in severity from alopecia to miliary dermatitis to ulcerated plaques or granulomas.
Diagnosis Rule out other causes of claw problems, especially infectious pododermatitis and neoplasia. Control external parasites. A good choice is fipronil as this controls fleas, and anecdotally mites (Cheyletiella, Sarcoptes, Otodectes and Notoedres) and provides partial control of ticks. Try a dietary trial using a food source that the cat has not been exposed to before. It may take ingenuity to find a new food that the cat is willing to eat. Duck, venison or rabbit (2/3 cup) with cooked rice or pasta (1/3 cup) are often tolerated. A trial period of a minimum of 9 weeks has been advocated for cats and up to 16 weeks preferably. Re-challenge the cat with the old diet to confirm the diagnosis, although owners may be unwilling to risk signs recurring. Intradermal skin testing to test for atopy. This is technically more difficult in cats than dogs, as reactions are less intense and more transient.
PRIMARY AND SECONDARY NEOPLASIA* Classical signs ● ●
Clinical signs Atopy and adverse food reactions result in various other dermatological manifestations such as ulcerated plaques, miliary dermatitis, symmetrical alopecia and pruritis of the face and neck.
Swollen, painful digit(s) and/or paronychia. Ulcerative destructive lesion of the paw and digits.
Pathogenesis Neoplasia involving the foot is rare in cats and is usually seen in older cats. The neoplasia may be primary
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or secondary. Secondary neoplasia results from metastasis of primary neoplasia in other organs. Squamous cell carcinoma. ● Rare primary tumor arising from the nail bed epithelium. ● Appears to be more aggressive than squamous cell carcinomas in other parts of the body. ● On clinical examination it may be mistaken for paronychia or pyoderma. Metastatic digital (ungual) carcinoma. ● Usually presents as lameness associated with multicentric digital carcinoma. ● Seen in aged cats (average age 13 years) with asymptomatic bronchogenic carcinoma or squamous cell carcinoma of the lung. ● Lesions can involve a number of digits and more than one paw. Typically there is swelling of the digit, ulceration of the skin or purulent discharge, and either fixed exsheathment, deviation or loss of the nail. Fibrosarcoma. ● Seen in older cats and is not associated with feline sarcoma virus. ● Lesions are usually solitary and can involve the digits. ● The area is alopecic, ulcerated and the tumor has rapid infiltrative growth. Undifferentiated sarcoma. ● Seen in older cats and involves the footpads of one or more feet. ● Affected pads are soft, mushy, painful and maybe ulcerated. Malignant fibrous histiocytoma. ● Seen in older cats. ● The lesions are solitary, firm, poorly circumscribed, variable in size and shape and locally invasive. ● Legs, especially the paw, and shoulders are the most common sites.
Bacterial or fungal infections, especially the rarer opportunistic ones, can look very similar. Biopsy for histopathology and culture will distinguish between these.
Treatment Radical surgical excision is the treatment of choice for tumors without evidence of metastasis. Mean survival for metastatic digital carcinoma was 67 days.
PEMPHIGUS* Classical signs ● ● ●
Crust, scales, alopecia in a symmetrical pattern. Areas usually involved are face, ears, trunk, feet and mucocutaneous junctions. Occasionally have only foot lesions.
Pathogenesis Pemphigus is an immune-mediated disease, with auto-antibodies directed against intercellular cement in the epidermis causing loss of cohesion between keratinocytes and resulting in the formation of bullae. ● Bullae are very transient in cat skin due to the thin epidermis, and may not be observed. What initiates the auto-antibodies is unknown, but drugs and chronic skin disease have been implicated in some cases. Different types of autoimmune dermatitis may involve cats’ paws but the most common is Pemphigus foliaceus.
Clinical signs Diagnosis Biopsy of representative areas and histopathology.
Differential diagnosis Plasma cell pododermatitis also has swollen mushy pads, which may be ulcerated.
Erythema, oozing, crusts, scales and alopecia occur with a symmetrical pattern on the face, ears, trunk, feet and mucocutaneous junctions. Lesions commonly involve the feet and footpads, causing hyperkeratosis and ulceration. Some cats are presented with only footpad lesions and sometimes lameness.
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Paronychia and involvement of the nipples are commonly seen in cats.
Diagnosis
Prognosis Prognosis is guarded, because the inciting cause is usually unknown, and the side effects of the therapy are often severe.
Direct smears from intact vesicles or pustules may show numerous acantholytic keratinocytes; these are strongly suggestive of pemphigus. Biopsy of primary lesions or at the periphery of the most recent lesions shows subcorneal pustules consisting of acantholytic keratinocytes and neutrophils. Direct immunofluorescence of biopsies shows diffuse intercellular fluorescence.
VARIATION IN NUMBER OF DIGITS* Classical signs ● ●
Abnormal number of toes (six most common). Agenesis or fusion of digits.
Differential diagnosis Systemic lupus erythematosus is rare and usually also has systemic signs. Insect hypersensitivity is common, but lesions are usually confined to the bridge of the nose, tips of the ears, and occasionally footpads. Seasonal occurrence and history of biting insects being observed around the cat helps differentiate this from pemphigus.
Treatment Therapy is often difficult as side effects from the drugs are common. High doses of glucocorticoids (4–8 mg/kg daily) will induce remission in most cases (about 2 weeks). Once in remission, reduce to alternate day therapy and to the minimum dose which maintains remission. Chlorambucil (0.1–0.2 mg/kg every 24–48 hours) can be added if glucocorticoids are insufficiently effective. Chrysotherapy (gold salts; aurothioglucose: Solganal; Schering) has been useful in cats when other treatments have failed. Begin with 1 mg/kg IM weekly until remission, which may take up to 12 weeks to occur. If no response is evident after 12 weeks of therapy, increase dose to 1.5–2 mg/kg. Once the cat responds, give the dose every 2 weeks and then monthly for several months. Alternatively the dose can be started at 0.25 mg/kg IM for the first week, 0.5 mg/kg the second week, then 1 mg/kg weekly until remission and then a gradually decreasing dosage.
Clinical signs Variation in the normal number of digits is present from birth. Ectrodactyly is agenesis of all or part of a digit and is an inherited defect involving the fore-paws. Polydactyly refers to extra toes. ● The mode of inheritance is dominant. ● There is considerable variation from animal to animal with the number of extra toes and how perfectly formed they are. ● Usually there are six toes on each front foot, but sometimes there can be seven toes on the front feet and six on the hind feet. The hind feet are not affected unless the front feet are involved. ● The incidence varies with it being common in some countries and not seen in others. Syndactyly refers to fusion of the digits. It is also called “split-foot” or “lobster-claw”. ● Typically it manifests as a central cleft of either one or both front feet. However, there may be fusion of the bones of the foot to produce double claws. ● The evidence is for dominant heredity, possibly with variable expression, as the number of affected animals is less than expected, with some genetically affected animals appearing normal. The right side tends to be more severely affected than the left.
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IRRITANT CONTACT DERMATITIS OR CHEMICAL BURNS* Classical signs ● ● ●
Variable erythema, ulceration, necrosis of the contact areas. Hyperkeratosis and scaling. Salivation and saliva staining around the mouth and paws with chemical burns.
Pathogenesis Irritant contact dermatitis or chemical burns are commonly caused by chemicals used in the environment such as herbicides, garden fertilizers, fuel oil and other common household or cattery cleaning products and disinfectants including chlorine bleach (sodium hyperchlorite), strong alkalis, strong acids, pine oils, phenolic compounds and quaternary ammonium compounds. Chemical burns with ulceration may occur if the product is incorrectly diluted. ● Typically this occurs if the product is applied undiluted and then water is used to dilute and wash the chemical away. Highly concentrated product may remain in less accessible areas, causing chemical burns to the feet and mouth. ● Signs develop when the cat inadvertently walks on them. Most common in cats living outdoors.
Clinical signs Typically, there is erythema and ulceration of the footpads, interdigital spaces and around the nails. Usually more than one paw is affected.
Diagnosis Diagnosis is based on history and physical examination.
Treatment Bathe to remove traces of offending chemical. Corticosteroids (prednisolone, 0.5–1 mg/kg PO q 24 h) to reduce inflammation. Non-steroidal antiinflammatory drugs can be given for pain relief and to reduce inflammation. Ketoprofen is registered for use in cats (2 mg/kg SC or PO initially then 1 mg/kg PO daily). Meloxicam (0.2 mg/kg SC or PO initially then 0.025 mg/kg PO 2–3 times/week. Antibiotics, if there is secondary infection. Protective dressings may be necessary if ulceration is severe to promote healing.
BURNS (THERMAL)* Classical signs ● ● ●
Initially the skin may be dry and hard. Necrotic skin sloughs leaving large raw areas. Purulent discharge when secondarily infected.
Pathogenesis Burns occur when cats walk or jump onto hot surfaces such as barbecues or stove hot plates, usually with the intent of stealing food. More generalized burns occur in cats trapped in house fires.
Pain and pruritis are sometimes evident. Oral ulcers and salivation are often present, and result from the cat licking its feet. Regurgitation may result from chemical esophagitis. Less toxic chemicals or concentrations may cause erythema, and excessive licking of the feet rather than ulceration.
Clinical signs Signs depend on the severity of the burn, and include superficial to deep ulceration and sloughing of the burnt area. Initially the skin may be dry and hard. Necrotic skin sloughs leaving large raw areas.
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Purulent discharge occurs when the burnt area becomes secondarily infected.
Treatment Silver sulfadiazine cream or aloe vera gel applied under a non-adherent dressing are excellent topical treatments for burns.
Clinical signs Frostbite typically affects the tips of the ears and the digits, areas that are not well insulated. Whilst frozen, the skin appears pale and cool to touch, and has decreased sensation. After thawing, there may be mild erythema, edema and pain.
Burn healing is slow, taking weeks to months of treatment.
In severe cases, the skin becomes necrotic and sloughs.
Very extensive or deep burns may heal with scarring that interferes with function, necessitating reconstructive surgical procedures.
Treatment
DECLAWING COMPLICATIONS Classical signs ● ●
Claw deformity or keratinaceous growths at the end of the digits. Swollen ends of digits and draining tracts.
Clinical signs Regrowth of claws may result from persistent germinative epithelium after incomplete removal during declawing.
Rapidly thaw frozen area by the gentle application of warm (42–44˚C) water. Handle tissues gently to prevent further damage and pain. Aloe vera gel applied topically helps to prevent vasoconstriction and tissue hypoxia. Any resulting necrotic areas may need surgical debriding. Antibiotics may be needed to control secondary infection, in cases where there is extensive tissue damage.
Regrowth can vary from deformed claws to keratinaceous foreign bodies at the ends of the digits.
FOREIGN BODIES
Swollen ends of digits and draining tracts may develop.
Classical signs ●
Nodules, abscess and draining tracts.
Diagnosis A history of a declawing procedure having been performed. Excisional biopsy of deformed ends of the digits is diagnostic and curative.
FROSTBITE
Clinical signs Objects such as plant awns, thorns can become embedded in the interdigital space. This is much rarer in cats than in dogs. Nodules, abscesses and draining tracts result.
Classical signs ● ● ●
Frozen skin is pale and cool to the touch. Mild erythema, edema and pain after thawing. Necrosis and sloughing in severe cases.
Treatment Surgical debridement and removal of foreign body. Use antibiotics if secondary infection develops.
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SYSTEMIC LUPUS ERYTHEMATOSUS Classical signs ● ●
Multi-systemic disease including the skin. Generaliszd or localized erythematous, scaly or crusted skin lesions.
Clinical signs Dermatological signs occur in 20–30% of cases. ● Typically, there are generalized or localized scaly or crusted lesions on the face, ears and eyelids. Alternatively, ulcerative lesions may be present on the face, trunk and feet. Periocular leukotrichia may be evident. ● Paronychia and oily seborrhea may occur. Systemic signs include intermittent pyrexia, anorexia, depression and weight loss. Involvement of other organs may result in immunemediated anemia, thrombocytopenia, glomerulonephritis and polyarthritis.
Diagnosis Definitive diagnosis is very challenging, as the disease is so variable in its clinical presentation. Skin biopsies show hydropic interface dermatitis.
Often there is seborrhea sicca and a dry, lusterless hair coat, which is easily epilated, and has poor regrowth after clipping. The skin may be myxoedematous and thickened. Other signs of hypothyroidism may be present including lethargy, inappetence, obesity, hypothermia and bradycardia. Most commonly occurs after bilateral thyroidectomy for hyperthyroidism. Spontaneous hypothyroidism is very rare.
Diagnosis If available, the thyroid stimulation test shows minimal to no stimulation. Free T4 or free T4 by equilibrium dialysis are below the normal values for the laboratory. Response to trial therapy with thyroxine (0.05–0.1 mg once daily) for 4 weeks results in improved clinical signs.
HYPERADRENOCORTICISM Classical signs ●
A high positive ANA titer may occur in some cats.
●
Laboratory results demonstrating multi-systemic disease suggest a tentative diagnosis of SLE.
●
HYPOTHYROIDISM
Pot-bellied appearance and muscle wasting. Unkempt hair coat with thin, easily torn skin. Polydypsia/polyuria and often associated diabetes mellitus (80% of cases).
See main reference on page 251 for details (The Cat With Polyuria and Polydipsia).
Classical signs ● ●
Lethargy, inappetence, obesity. Seborrhea sicca and a dry, lusterless hair coat, easily epilated with poor regrowth.
Clinical signs Hypothyroidism may result in erythematous, scaling and papular lesions, which affect the forehead, abdomen, tail and footpads.
Clinical signs Bilaterally symmetrical alopecia involving the face, flanks and limbs. The skin is often very thin and easily torn especially on the digits. Systemic signs of polydypsia, polyuria and weight loss are usually associated with diabetes mellitus.
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Diagnosis Low-dose dexamethasone test (0.1 mg/kg) or ACTH stimulation test is used for diagnosis. Imaging the adrenals by abdominal ultrasound helps differentiate pituitary from adrenal-dependent hyperadrenocorticism.
DIABETES MELLITUS Classical signs ●
Polydypsia, polyuria, polyphagia and weight loss.
See main reference on page 236 for details (The Cat With Polyuria and Polydipsia).
Vitiligo is a hereditary lack of pigment in the skin, and may have an autoimmune pathogenesis. ● Three affected Siamese cats had antimelanocyte antibodies, whereas four normal Siamese cats did not. ● There can be symmetric macular depigmentation, especially of the nose, lips, buccal mucosa and facial skin, also footpads and claws. ● Lesions are most noticeable in the dark coat colors where the normally dark footpads have pink patches. ● Onset of the condition is usually in young adulthood.
Diagnosis
Clinical signs
Diagnosis is based on the history of a young age with patches of unpigmented skin in normally darkpigmented areas.
Cutaneous xanthomatosis has been described in cats with diabetes mellitus.
In vitiligo there is no history of trauma or inflammation that could have damaged melanocytes.
This may present as whitish, waxy nodules in the paws. Typical signs include polydypsia, polyuria, polyphagia and weight loss.
CUTANEOUS HORNS Classical signs ●
Firm, horn-like protuberance on the skin.
Diagnosis A tentative diagnosis is based on a history of polydypsia and polyuria with weight loss.
Pathogenesis
A definitive diagnosis is based on demonstrating persistent hyperglycemia > 12 mmol/L (> 216 mg/dl).
The term cutaneous horn is used to describe a keratotic mass that is generally higher than it is wide, usually several millimeters in diameter and 1–2 cm high.
HYPOMELANOSIS (VITILIGO)
Cutaneous horn of the footpads in cats is a rare disorder. Affected cats have been positive for FeLV and the virus has been isolated from the horn material.
Classical signs ●
Patches of complete lack of pigment.
The viral-affected horns occur on the footpads only.
Clinical signs
Clinical signs
Loss of epidermal pigmentation (hypomelanosis) can be primary as with vitiligo, or secondary as in postinflammatory change.
Single or multiple firm horn-like formations arising from any area of skin. Footpads seem to be predisposed sites.
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Diagnosis Diagnosis is based on the typical clinical appearance and histopathology of dense laminated hyperkeratosis. Biopsy may be necessary to check for squamous cell carcinoma at the base. Check FeLV status.
Treatment Surgical excision is the treatment of choice. Recurrences are frequent.
CALCINOSIS CUTIS Classical signs ● ● ●
Enlarged, painful and firm pads. The pads may be ulcerated and exuding a white paste of gritty material. Signs of chronic renal disease.
See main reference on page 245 (The Cat With Polyuria and Polydipsia).
Clinical signs Calcinosis cutis is a rare complication of chronic renal disease. Affected pads are enlarged, firm and painful. A chalky white-to-pink material with feathery margins may be seen through the intact epidermis of nonulcerated lesions. Older lesions may ulcerate and extrude a chalky, white, pasty to gritty material. Other signs associated with chronic renal disease such as polyuria/polydypsia, and weight loss.
EPIDERMOLYSIS BULLOSA Classical signs ● ● ●
Uncommon congenital disorder. Avulsion of the claws with minor trauma. Erosive lesions on the hard palate.
Pathogenesis Separation of epidermal tissues from the dermis occurs after minor trauma because of defective adherence of the dermo–epidermal junction. Epidermolysis bullosa is an uncommon congenital disorder, that has been reported in a line of Siamese cats.
Clinical signs Nails are shed after minor trauma. The entire claw is avulsed, leaving the corium quick exposed. Regrown claws may be deformed. There may also be ulcers on the footpads and hard palate. The onset is noticed when kittens become ambulatory and start climbing. Lesions may have secondary bacterial infection.
Diagnosis A definitive diagnosis is based on histopathology of an amputated P3 which demonstrates dermo– epidermal separation without inflammation or basal cell injury.
Diagnosis
Differential diagnosis
A definitive diagnosis is based on biopsy of the lesion that demonstrates metastatic calcium deposition in the tissues.
Bacterial paronychia can be very similar, but the history and histopathology will differentiate.
Clinical and laboratory findings are consistent with chronic renal failure.
Immune-mediated disease affecting the claws, but generally there are severe dermatological signs elsewhere on the body.
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Treatment Curative treatment is not available, but amputation of P3 of affected digits will prevent recurrent claw loss with associated pain and infection. Secondary infection should be managed with suitable antibiotics. Avoid trauma.
ARTERIOVENOUS FISTULAE Classical signs ● ●
Localized persistent or recurrent edema. Distinct and tortuous blood vessels near the area.
THALLIUM POISONING Classical signs ● ● ● ●
Easily epilated hair. Cutaneous erythema, erosions, crusts, necrosis and alopecia. Lesions on ears, nose, abdomen. Marked redness of mucous membranes.
Pathogenesis Thallium is a cumulative rodenticide rapidly absorbed through the mucosae and skin. Its use is now banned in many countries.
Clinical signs Pathogenesis Arteriovenous fistulae are traumatically induced from penetrating wounds, blunt trauma or post-surgical complications of onychectomy.
Skin lesions are seen in association with chronic toxicity, and are characterized by chronic dermatitis. There is severe redness of mucous membranes, cutaneous erythema, erosions, crusts, necrosis and alopecia. Lesions are usually present around body orifices and on the nose, ears, abdomen and feet. The footpads become hyperkeratotic and ulcerated.
Clinical signs
Hair is easily epilated.
Arteriovenous fistulae may be associated with persistent or recurrent edema and bacterial paronychia of one paw.
Diagnosis
Pulsating blood vessels, palpable thrills and continuous machinery murmurs are present in the area of the fistula.
Diagnosis is based on a history of exposure to thallium and positive test for thallium in the urine. Skin biopsies demonstrate dermatitis consistent with thallium poisoning.
Diagnosis
Differential diagnosis
A tentative diagnosis is based on the clinical signs.
A number of diseases can have a similar crusted and ulcerated appearance, and distribution to thallium toxicosis, and skin biopsies are needed to differentiate. These include: ● Autoimmune disorders. ● Drug eruptions. ● Erythema multiforme and toxic epidermal necrolysis. ● Lymphoreticular neoplasia.
Definitive diagnosis is by demonstration of the fistula by contrast radiography.
Treatment Surgical removal of the fistula or amputation of the affected part.
53 – THE CAT WITH PAW OR PAD PROBLEMS
Treatment Prussian blue (100 mg/kg IV) given daily until urinary tests for thallium are negative has been used to treat thallium toxicosis, but is relatively ineffective when clinical signs are already present. The recommendation at present is combination treatment with charcoal for gastrointestinal trapping of thallium and potassium chloride supplementation
(1–2 g q 8–12 h) to promote renal excretion of thallium. Supportive care such as intravenous fluids and antibiotics for secondary infection.
Prognosis Prognosis is very guarded, and most cases die.
RECOMMENDED READING Bertazzolo W, Toscani L, Calcaterra S, Crippa L, Caniatti M, Bonfanti U. Clinicopathological findings in five cats with paw calcification J Feline Med Surg 2003; 5: 11–17. Dias-Pereira P; Faustino A. Feline plasma cell pododermatitis: a study of 8 cases. Vet Dermatol 2003; 14: 333–337. Foil CS. Facial, pedal, and other regional dermatoses. Vet Clin North Am Small Anim Pract 1995; 25: 923–944. Guaguere E, Hubert B, DeLabre C. Feline dermatoses. Vet Derm 1992; 3: 1–12. Scott DW, Miller WH Jr, Disorders of the claw and clawbeds in cats. Comp Cont Educ 1992; 14: 449–455. Scott DW, Miller WH Jr, Griffin CE. Muller and Kirk’s Small Animal Dermatology, 5th edn. 1995.
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