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Microsporidial keratitis: Literature review and report of 2 cases in a tertiary eye care center
Saudi Journal of Ophthalmology (2012) 26, 199–203
Ophthalmic Pathology Update
Microsporidial keratitis: Literature review and report of 2 cases in a tertiary eye care center Hind M. Alkatan, MD a,⇑; Sultan Al-Zaaidi, MD b; Sreedharan Athmanathan, MD a
Abstract Microsporidia are getting more recognized as causative organism of ocular, gastrointestinal, renal, pulmonary, and sinus diseases, in both immunocompetent and immunosuppressed patients. Ocular microsporidiosis can be isolated or may present as part of systemic infection. Recent reports showed increasing number of cases of ocular microsporidiosis in immunocompetent individuals. The ocular type occurs mainly in two forms: keratoconjunctivitis form which is mostly seen in immunocompromised individuals and stromal keratitis form seen in immunocompetent individuals. The ocular cases which present with superficial keratitis in acquired immune deficiency syndrome (AIDS) patients differ from the cases seen in immunocompetent individuals which present mainly as deep stromal keratitis. We are presenting the only two documented cases of microsporidial keratitis diagnosed over 25 years of practice in our institution. The cases are diagnosed by identification of the Acid-fast organisms. Ultrastructure and additional information on species identification in one of the cases. Both cases are eventually managed by therapeutic PKP. Diagnosis and treatment modalities are discussed based on a comprehensive literature review. Keywords: Microsporidia, Stromal keratitis, Keratoconjunctivitis Ó 2012 Saudi Ophthalmological Society, King Saud University. All rights reserved. doi:10.1016/j.sjopt.2012.02.007
Introduction
Case 1
Microsporidia are small eukaryotic, spore forming obligate intracellular parasites, first recognized over 100 years ago.1 The first case of corneal microsporidiosis was published by Ashton in 1973.2 They are getting more recognized as infectious pathogens causing ocular, sinus, renal, intestinal, pulmonary, and muscular diseases, in both immunocompetent and immunosuppressed patients.3,4 Ocular features of this type of infection can either represent corneal stromal keratitis which mainly affects immunocompetent patients or superficial punctuate keratoconjunctivitis which usually affects AIDS patients or contact lens wearers,4–6 We have encountered two cases of microsporidial keratitis in our tertiary eye care center. Both cases are presented with histopathologic and ultrastructural confirmation of the diagnosis. They were both managed by therapeutic penetrating keratoplasty (PKP).
A 42-year-old Saudi male who is a known diabetic presented to King Khaled Eye Specialist Hospital (KKESH) with 6 months history of right eye redness and pain. He denied history of trauma or previous similar episodes. Initial ophthalmic examination of the right eye revealed visual acuity (VA) of counting figures at half foot and intraocular pressure (IOP) of 11 mm Hg. He had an epithelial defect with stromal infiltrate and edema inferiorly. Corneal sensation was intact. The Anterior chamber shower 1+ flare and 1+ cells. His preliminary diagnosis was herpetic keratitis. The microtrack for herpes simplex virus (HSV) was negative however, he did respond to Valcyclovir ‘‘Valtrex’’ 500 mg twice daily and Vigamox eye drops every 4 h in the right eye. One month later he presented with painful red right eye with reduced VA to hand movement and a large corneal abscess measuring
Received 18 January 2012; accepted 8 February 2012; available online 16 February 2012. a b
Pathology and Laboratory Medicine Department, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia Anterior Segment/Uveitis Division, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia
⇑ Corresponding author. Address: Senior Consultant and Chair of Pathology and Laboratory Medicine Department, King Khaled Eye Specialist Hospital, P.O. Box 7191, Riyadh 11462, Saudi Arabia. Tel.: +966 1 4821234x3131; fax: +966 1 2052740. e-mail addresses: [email protected], [email protected] (H.M. Alkatan). Peer review under responsibility of Saudi Ophthalmological Society, King Saud University
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Production and hosting by Elsevier Access this article online: www.saudiophthaljournal.com www.sciencedirect.com
200 7.5 8.7 mm (Fig. 1(A)). He was started again on the same medications with no improvement. Therapeutic PKP was performed (9 and 10 mm) combined with Anterior chamber washout with ceftazidine and vancomycin. Half of the right eye corneal tissue obtained was sent to microbiology for culture in addition to Gram, Giemsa, and Calcofluor stains which showed organisms resembling microsporidia and no fungal growth. The other half was sent for histopathology which showed acute stromal keratitis with necrosis and acid fast organisms resembling spores of Microsporidium (Fig. 1(B)). Electron microscopy (EM) confirmed the presence of microsporidia (Fig. 1(C) and (D)). The indirect immuno-fluorescence testing was performed in a referral laboratory facility and was positive for Encephalitozoon species. The patient did well after surgery with a clear graft and no evidence of recurrence and VA of 20/200 (with best corrected vision of 20/40) with a follow up period of 2 years. Then he developed another attack of right keratitis with negative cultures of the corneal scraping. The last attack resolved by oral Valtrex 500 mg twice daily, in addition to topical Vigamox and Predforte drops. He ended up with a failed graft, however, no further surgical intervention was performed up to his last follow up in November 2011.
Case 2 A 53-year-old Saudi female who is known to have diabetes and hypertension. She presented to KKESH with a 3 month history of pain, redness and reduced vision in her right eye. Initial evaluation of that eye revealed lid swelling, severe ciliary injection, and corneal epithelial defect with an abscess. No VA was documented in the initial visit. The Anterior chamber findings were not mentioned and the posterior pole was not visualized at presentation. The patient underwent therapeutic PKP for her right eye. The half corneal tissue sent to microbiology for staining showed beaded organisms by Giemsa stain and the culture was negative for fungal growth.
H.M. Alkatan et al. Histopathology of the remaining corneal tissue revealed acute stomal keratitis, negative GMS stain and acid fast organisms consistent with Microsporidium (Fig. 2(A) and (B)). EM showed several structures resembling microsporidia (Fig. 2(C)). The patient did well for one year then developed signs of graft failure with iris adhesions (Fig. 2(D)). Her VA dropped to HM near the face and was offered a second PKP which was declined by the patient in her last follow up in September 2010.
Discussion Ocular microsporidiosis can be isolated or can occur as a part of systemic infection. Two main forms are recognized: a form which is mostly seen in immune-compromised individuals and presents as keratoconjunctivitis and the other form which usually affects immunocompetent individuals and presents as stromal keratitis.5,6 More cases have been reported in the late 80s7,8 Currey reported one case of bilateral microsporidial keratitis following infection by an insect parasite from the genus Nosema.9 Vemuganti reported a case series of five patients of microsporidial stromal keratitis from South India.10 The keratoconjunctivitis form of the disease has been reported in both the seronegative HIV patients and healthy individuals.11,12 Currently microsporidia are recognized as an opportunistic infection in the immunocompromised patients. The source of infection is thought to be either orofaecal, resulting from direct inoculation, or occurring after trauma.5 Direct inoculation may occur with close contacts representing spread from other infected persons13,14 or following contact with domestic animals such as cats and birds.9,15 The normal life cycle of microsporidia comprises of invasion of the spore into the human host cell followed by discharge of the contents into the cytoplasm .Within the cell the sporoblast divides by binary fission to form scizont with 2–6 nuclei, which split into unicellular meronts .The meronts
Figure 1. (A) The clinical appearance or the right eye corneal abcess in case 1; (B) The appearance of typical microsporidia. (Acid fast stain, original magnification x1000); (C and D) Transmission electron microscopy of microsporidia in the same case (Original magnification x12 K).
201
Microsporidial keratitis: Literature review and report of 2 cases
Figure 2. (A) Histopathology of the acute stromal keratitis in case 2 (Hematoxylin and eosin, original magnification x100); (B) Similar appearance of microsporidia organisms within the stroma (Acid fast stain, original magnification x1000); (C) Transmission electron microscopy of structures resembling microsporida (Original magnification x8000); (D) The clinical appearance of the right eye with a failed corneal graft after 1 year.
then secrete a rigid capsule and the fully formed spore measures about 2.5 1.5 microns. The cell eventually ruptures to continue the cycle and further destruction of the host tissue.16
Microbiology facts In infectious diseases, the isolation techniques and identification tools provide rapid determination of the causative organism, the problem with microsporidia is that they are obligate intracellular parasites requiring cell culture systems for growth. Therefore, the diagnosis mainly depends on morphological demonstration of the organisms themselves in scrapings or tissues. Microsporidia are small (3.5–5.0 lm by 2.0–3.0 lm), oval obligate intracellular eukaryotic protozoan parasites that belong to phylum Microspora. More than 100 species have been classified into approximately 100 genera, and about 13 species have been reported to infect mammals.4,13–15 Phylogenetically microsporidia are early eukaryotic organisms because they have a true nucleus, possess prokaryotic like ribosome and lack mitochondria. 14 Joseph reviewed the disease and named four genera that infect humans Encephalitozoon, Nosema, Pleistophora and Enterocytozoon.6 Other reports showed that seven genera (Enterocytozoon species, Brachiola species, Encephalitozoon species, Pleistophora species, Nosema species, Vittaforma species and Trachipleistophora species) as well as unclassified microsporidia (collectively referred to as Microsporidium) have been associated with human disease involving immunocompromised patients.4,13–15 Microsporidia have developed a specific process to infect their host which takes place in vitro.17 It involves spore activation and polar tube discharge, by which the infective sporoplasm is injected into the host cell cytoplasm.18 It is followed by immediate breakdown of sporoplasm compartmentalization, producing an increase in osmotic pressure
which triggers polar tube eversion and injection of the sporoplasm into the host cell.18
Clinical features Ocular features of this type of infection can either represent corneal stromal keratitis which mainly affects immunocompetent patients and is commonly caused by Nosema corneum4 or superficial punctuate keratoconjunctivitis which usually affects acquired immune deficiency syndrome (AIDS) patients or contact lens wearers, in which cases are mostly caused by genus Encephalitozoon. Keratoconjuctivitis may also affect immunocompetent humans. Microsporidial keratitis in healthy persons can mimic herpetic keratitis with history of recurrent redness, pain, photophobia, watering, and decreased vision. Such cases may be mistaken and treated with antiviral and topical steroids which were documented in the management history of our first case. The clinical findings include lid edema, congested conjunctiva and corneal lesions. The corneal involvement is usually in the form of mid to deep stromal infiltrates surrounded by edema with either intact epithelium and/or epithelial defect over the stromal lesions. The endothelium does not show precipitates.
Diagnosis Microsporidia are small, obligate intracellular parasites that produce infective spores. They are fastidious organisms that are difficult to culture. The organism can be isolated using special tissue culture techniques, which are available only in few specialized laboratories, and hence routine microbiological diagnosis might be difficult.19,20 Alcohol-fixed cytologic samples of scrapings from the conjunctiva, corneal epithelium, or both as well as biopsy specimens are proven to be very useful for demonstrating microsporidial blastospores.8,21
202 The light microscopy has greatly improved lately in diagnosing microsporidiosis. Conjunctival scrapings alone can provide a satisfactory specimen for cytologic diagnosis in microsporidial epithelial punctuate keratoconjunctivitis. Cytologic findings demonstrate small, oval organisms within the epithelial cells, stromal keratocytes, and histiocytes as well as free extracellular structures.22–24 These spores have uniform oval shape and are non-budding, which helps to differentiate them from bacteria and yeasts.25 The spores stain strongly with gram stain.26,27 Giemsa and 1% acid fast stains have also been successfully used to demonstrate microsporidial spores.22,23 Occasionally, these spores stain poorly or not at all with routine stains (hematoxylin/eosin or the Papanicolaou methods), with the organism being easily overlooked in biopsy specimens or cytologic preparations.25,28 Definitive diagnosis and species differentiation may necessitate EM studies. This has been used for ocular infections by examination of tissue biopsy from cornea or conjunctiva using electron microscope to demonstrate the number of coils of the filament.22–24,26–28To differentiate between Nosema species and Encephalitozoon several electron microscopic features can be identified. In Nosema the coils of the filament range from 11 to 13 in Nosema versus 4–7 in Encephalitozoon. The Nosmea are larger than Encephalitozoon; also the absence of a parasitophorous vacuole surrounding the organism within the host cell is more consistent with Nosema.16 Immuno-fluorescent staining techniques are advanced tools which need specific antibodies only available in research laboratories. This was performed for our first case for identification of the organism which belongs to Encephalitozoon species. In the last few years, the use of molecular techniques has been developed for the detection and species differentiation of microsporidia.
H.M. Alkatan et al. Secondary infection and penetration of the organisms into the deeper stroma may follow corneal scrapings, use of topical steroids or bandage contact lenses.23 In case where the medical treatment fails PKP has been recommended rather than lamellar graft to treat deep stromal microsporidiosis to avoid any chance of recurrence in the lamellar bed.10 However, deep anterior lamellar keratoplasty has been also recently considered as an option for visual rehabilitation.39
Conclusion Microsporidia are an important cause of disease in both HIV and non-HIV patients with or without immunosuppression. High index of suspicion is needed for prompt diagnosis and treatment. Therefore, ophthalmologists should consider microsporidia in the differential diagnosis of infectious keratitis.40 As diagnosis by conventional methods is still challenging and may need an advanced laboratory tools such as EM, newer methods such as molecular biology (PCR) or serology methods should be developed to be utilized for the diagnosis and species differentiation of microsporidia which may have important implication in the management. Being uncommon or being overlooked again necessitates careful study of this organism and its microbiological behavior. This also makes the judgment on current therapeutics incomplete. Many treatment modalities for ocular microsporidiosis have been suggested in the literature including scraping, bandage contact lenses, steroids, and antimicrobial agents with successful outcome in selected cases. Fumagillin has shown to be an effective medical treatment while PKP is the preferred alternative surgical management.
Treatment
Acknowledgment
So far there is no known definitive medical treatment of deep microsporidial corneal stromal infections. Some previous reports have suggested that treatment with topical propamidine isethionate 0.1% (Brolene)28,29or systemic itraconazole19 which might be effective against microsporidial superficial keratoconjuctivitis. Subjective improvement was reported with debulking and a combination of topical neomycin, polymyxin B and bacitracin antibiotics in a patient with bilateral epithelial keratopathy caused by Encephalitozoon; while complete resolution was achieved only after administration of oral itraconazole.22 Successful treatment of microsporidial superficial keratoconjuctivitis with topical fumagillin has been also reported.30–35 Fumagillin is a naturally secreted water-insoluble antibiotic of Aspergillus fumigatus and is noted to possess an inhibitory effect on some intestinal protozoa.34 Fumagillin bicyclohexylammonium salt is the water soluble form of fumagillin used commercially. The mechanism of action of fumagillin is not clearly understood but it may alter DNA content or inhibit RNA synthesis in the organism.36,37 Some authors have also suggested the role of oral albendazole in combination with topical fumagillin. Others have shown good response to medical treatment with systemic albendazole and topical chlorhexidine in a selected case where the infection is limited to the mid-stroma.38
This project is approved by the institutional review board (IRB) and human ethics committee (HEC) at KKESH.
References 1. Nageli KW. Uber die neue krankheit der seidenraupe und verwandte organismen. Bot Z 1857;15:760–1. 2. Ashton N, Wirasinha PA. Encephalitozoonosis of the cornea. Br J Ophthalmol 1973;57:669–74. 3. Franzen C, Muller A. Molecular techniques for detection, species differentiation and phylogenetic analysis of microsporidia. Clin Microbiol Rev 1999;12:243–85. 4. Weber R, Bryan RT, Schwartz DA, Owen RL. Human microsporidial infections. Clin Microbiol Rev 1994;7:426–61. 5. Das S, Sharma S, Sahu SK, Nayak SS, Kar S. New microbial spectrum of epidemic keratoconjunctivitis: clinical and laboratory aspects of an outbreak. Br J Ophthalmol 2008;92(6):861–2. 6. Joseph J, Vemuganti GK, Sharma S. Microsporidia: emerging ocular pathogens. Ind J Med Microbiol 2005;23(2):80–91. 7. Pinnolis M, Egbert PR, Font RL, Winter FC. Nosematosis of the cornea. Case report, including electron microscopic studies. Arch Ophthalmol 1981;99:1044–7. 8. Davis RM, Font RL, Keisler MS, Shadduck JA. Corneal microsporidiosis. A case report including ultrastructural observations. Ophthalmology 1990;97:953–7. 9. Curry A, Mudhar HS, Dewan S, Canning EU, Wagner BE. A case of bilateral microsporidial keratitis from bangladesh-infection by an insect parasite from the genus Nosema. J Med Microbiol 2007;56(9):1250–2.
Microsporidial keratitis: Literature review and report of 2 cases 10. Vemuganti GK. Is microsporidiosis keratitis an emerging cause of stromal kratitis – A case series study. BMC Ophthalmol 2005;32:44–5. 11. Sridhar MS, Sharma S. Microsporidial keratoconjunctivitis in a HIVseronegative patient treated with debridement and oral itraconazole. Am J Ophthalmol 2003;136:745–6. 12. Chan CM, Theng JT, Li L, Tan DT. Microsporidial keratoconjunctivitis in healthy individuals: a case series. Ophthalmology 2003;110:1420–5. 13. Shadduck JA. Human microsporidiosis and AIDS. Rev Infect Dis 1989;11:203–7. 14. Didier ES, Snowden KF, Shadduck JA. Biology of microsporidian species infecting mammals. Adv Parasitol 1998;40:283–320. 15. Shadduck JA, Greely E. Microsporidia and human infections. Clin Microbiol Rev 1989;2:158–65. 16. Kai S, Vanathi M, Panda A. Corneal Microsporidiosis. J K Science 2009;11(2):59–61. 17. Vossbrinck CR, Maddox JV, Friedman S, Debrunner-Vossbrinck BA, Woese CR. Ribosomal RNA sequence suggests microsporidia are extremely ancient eukaryotes. Nature 1987;5:411–4. 18. Bigliardi E, Sacchi L. Cell Biology and invasion of the microsporidia. Microbe Infect 2001;3:373–9. 19. Shadduck JA, Meccoli RA, Davis R, Font RL. Isolation of a microsporidian from a human patient. J Infect Dis 1990;162:773–6. 20. Didier ES, Didier PJ, Friedberg DN, et al. Isolation and characterization of a new human microsporidian, Encephalitozoon hellum from three AIDS patients with keratoconjunctivitis. J Infect Dis 1991;163:617–21. 21. Schwartz DA, Visvesvara GS, Diesenhouse MC, et al. Pathologic features and immuno-fluorescent antibody demonstration of ocular microsporidiosis in seven patients with acquired immunodeficiency syndrome. Am J Ophthalmol 1993;115:285–92. 22. Yee RW, Tio FO, Martinez JA, et al. Resolution of microsporidial epithelial keratopathy in a patient with AIDS. Ophthalmology 1991;98:196–201. 23. Friedberg DN, Stenson SM, Orienstein JM, et al. Microsporidial keratoconjunctivitis in acquired immunodeficiency syndrome. Arch Ophthalmol 1990;108:504–8. 24. Weber R, Kuster H, Visvesvara GS, et al. Disseminated microsporidiosis due to Encephalitozoon hellum: pulmonary colonization, microhematuria, and mild conjunctivitis in patient with AIDS. Clin Infect Dis 1993;17:415–9.
203 25. Schwartz DA, Sobottka I, Leitch GJ, et al. Pathology of microsporidiosis. Emerging parasitic infections in patients with the AIDS. Arch Pathol Lab Med 1996;120:173–88. 26. Lowder CY, Meister M, McMahon JT, et al. Microsporidia infection of the cornea in a man seropostive for HIV virus. Am J Ophthalmol 1990;109:242–4. 27. Diesenhouse MC, Wilson LA, Corrent GF, et al. Treatment of microsporidial keratoconjunctivitis with topical fumagillin. Am J Ophthalmol 1993;115:293–8. 28. McCluskey PJ, Goonan PV, Marriot DJ, Fields AS. Microsporidial keratoconjunctivitis in AIDS. Eye 1993;7:80–3. 29. Metcalfe TW, Doram RM, Rowlands PL, et al. Microsporidial keratoconjunctivitis in patient with AIDS. Br J Ophthalmol 1992;76:177–8. 30. Costa SF, Weiss LM. Drug treatment of microsporidiosis. Drug Resist Updat 2000;3:384–99. 31. Roseberger DF, Serdarevic ON, Erlandson RA, et al. Successful treatment of microsporidial keratoconjunctivitis with topical fumagillin in patient with AIDS. Cornea 1993;12:261–5. 32. Mccowen MC, Callender ME, Lawlis Jr JF. Fumagillin a new antibiotic with amebicidal properties. Science 1951;113:202–3. 33. Shadduck JA. Effect of fumagillin on in vitro multiplication of Encephalitozoon cuniculi. J Protozool 1980;27:202–8. 34. Killough JH, Magill GB, Smith RC. The treatment of amebiasis with fumagillin. Science 1952;115:70. 35. Katzneslon H, Jamieson CA. Control of nosema disease of honey bees with fumagillin. Science 1952;115:70–1. 36. Jaronski ST. Cytochemical evidence for RNA synthesis inhibition by fumagillin. J Antibiot 1972;25:327–31. 37. Hartwig A, Przelecka A. Nucleic acid in intenstine of Apis mellifica infected with Nosema apis and treated with fumagillin DCH: cytochemical and autoradiographic studies. J Invertebr Pathol 1971;18:331–6. 38. Sangit VA, Murthy SI, Garg P. Microporidial stromal keratitis successfully treated with medical therapy: a case report. Cornea 2011;30(11):1264–6. 39. Ang M, Mehta JS, Mantoo S, Tan D. Deep anterior lamellar keratoplasty to treat microsporidial stromal keratitis. Cornea 2009;28(7):832–5. 40. Sharma S, Das S, Joseph J, Vemuganti GK, Murthy S. Microsporidial keratitis: need for increased awareness. Surv Ophthalmol 2011;56(1):1–22.
Ophthalmic Pathology Update
Microsporidial keratitis: Literature review and report of 2 cases in a tertiary eye care center Hind M. Alkatan, MD a,⇑; Sultan Al-Zaaidi, MD b; Sreedharan Athmanathan, MD a
Abstract Microsporidia are getting more recognized as causative organism of ocular, gastrointestinal, renal, pulmonary, and sinus diseases, in both immunocompetent and immunosuppressed patients. Ocular microsporidiosis can be isolated or may present as part of systemic infection. Recent reports showed increasing number of cases of ocular microsporidiosis in immunocompetent individuals. The ocular type occurs mainly in two forms: keratoconjunctivitis form which is mostly seen in immunocompromised individuals and stromal keratitis form seen in immunocompetent individuals. The ocular cases which present with superficial keratitis in acquired immune deficiency syndrome (AIDS) patients differ from the cases seen in immunocompetent individuals which present mainly as deep stromal keratitis. We are presenting the only two documented cases of microsporidial keratitis diagnosed over 25 years of practice in our institution. The cases are diagnosed by identification of the Acid-fast organisms. Ultrastructure and additional information on species identification in one of the cases. Both cases are eventually managed by therapeutic PKP. Diagnosis and treatment modalities are discussed based on a comprehensive literature review. Keywords: Microsporidia, Stromal keratitis, Keratoconjunctivitis Ó 2012 Saudi Ophthalmological Society, King Saud University. All rights reserved. doi:10.1016/j.sjopt.2012.02.007
Introduction
Case 1
Microsporidia are small eukaryotic, spore forming obligate intracellular parasites, first recognized over 100 years ago.1 The first case of corneal microsporidiosis was published by Ashton in 1973.2 They are getting more recognized as infectious pathogens causing ocular, sinus, renal, intestinal, pulmonary, and muscular diseases, in both immunocompetent and immunosuppressed patients.3,4 Ocular features of this type of infection can either represent corneal stromal keratitis which mainly affects immunocompetent patients or superficial punctuate keratoconjunctivitis which usually affects AIDS patients or contact lens wearers,4–6 We have encountered two cases of microsporidial keratitis in our tertiary eye care center. Both cases are presented with histopathologic and ultrastructural confirmation of the diagnosis. They were both managed by therapeutic penetrating keratoplasty (PKP).
A 42-year-old Saudi male who is a known diabetic presented to King Khaled Eye Specialist Hospital (KKESH) with 6 months history of right eye redness and pain. He denied history of trauma or previous similar episodes. Initial ophthalmic examination of the right eye revealed visual acuity (VA) of counting figures at half foot and intraocular pressure (IOP) of 11 mm Hg. He had an epithelial defect with stromal infiltrate and edema inferiorly. Corneal sensation was intact. The Anterior chamber shower 1+ flare and 1+ cells. His preliminary diagnosis was herpetic keratitis. The microtrack for herpes simplex virus (HSV) was negative however, he did respond to Valcyclovir ‘‘Valtrex’’ 500 mg twice daily and Vigamox eye drops every 4 h in the right eye. One month later he presented with painful red right eye with reduced VA to hand movement and a large corneal abscess measuring
Received 18 January 2012; accepted 8 February 2012; available online 16 February 2012. a b
Pathology and Laboratory Medicine Department, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia Anterior Segment/Uveitis Division, King Khaled Eye Specialist Hospital, Riyadh, Saudi Arabia
⇑ Corresponding author. Address: Senior Consultant and Chair of Pathology and Laboratory Medicine Department, King Khaled Eye Specialist Hospital, P.O. Box 7191, Riyadh 11462, Saudi Arabia. Tel.: +966 1 4821234x3131; fax: +966 1 2052740. e-mail addresses: [email protected], [email protected] (H.M. Alkatan). Peer review under responsibility of Saudi Ophthalmological Society, King Saud University
j
Production and hosting by Elsevier Access this article online: www.saudiophthaljournal.com www.sciencedirect.com
200 7.5 8.7 mm (Fig. 1(A)). He was started again on the same medications with no improvement. Therapeutic PKP was performed (9 and 10 mm) combined with Anterior chamber washout with ceftazidine and vancomycin. Half of the right eye corneal tissue obtained was sent to microbiology for culture in addition to Gram, Giemsa, and Calcofluor stains which showed organisms resembling microsporidia and no fungal growth. The other half was sent for histopathology which showed acute stromal keratitis with necrosis and acid fast organisms resembling spores of Microsporidium (Fig. 1(B)). Electron microscopy (EM) confirmed the presence of microsporidia (Fig. 1(C) and (D)). The indirect immuno-fluorescence testing was performed in a referral laboratory facility and was positive for Encephalitozoon species. The patient did well after surgery with a clear graft and no evidence of recurrence and VA of 20/200 (with best corrected vision of 20/40) with a follow up period of 2 years. Then he developed another attack of right keratitis with negative cultures of the corneal scraping. The last attack resolved by oral Valtrex 500 mg twice daily, in addition to topical Vigamox and Predforte drops. He ended up with a failed graft, however, no further surgical intervention was performed up to his last follow up in November 2011.
Case 2 A 53-year-old Saudi female who is known to have diabetes and hypertension. She presented to KKESH with a 3 month history of pain, redness and reduced vision in her right eye. Initial evaluation of that eye revealed lid swelling, severe ciliary injection, and corneal epithelial defect with an abscess. No VA was documented in the initial visit. The Anterior chamber findings were not mentioned and the posterior pole was not visualized at presentation. The patient underwent therapeutic PKP for her right eye. The half corneal tissue sent to microbiology for staining showed beaded organisms by Giemsa stain and the culture was negative for fungal growth.
H.M. Alkatan et al. Histopathology of the remaining corneal tissue revealed acute stomal keratitis, negative GMS stain and acid fast organisms consistent with Microsporidium (Fig. 2(A) and (B)). EM showed several structures resembling microsporidia (Fig. 2(C)). The patient did well for one year then developed signs of graft failure with iris adhesions (Fig. 2(D)). Her VA dropped to HM near the face and was offered a second PKP which was declined by the patient in her last follow up in September 2010.
Discussion Ocular microsporidiosis can be isolated or can occur as a part of systemic infection. Two main forms are recognized: a form which is mostly seen in immune-compromised individuals and presents as keratoconjunctivitis and the other form which usually affects immunocompetent individuals and presents as stromal keratitis.5,6 More cases have been reported in the late 80s7,8 Currey reported one case of bilateral microsporidial keratitis following infection by an insect parasite from the genus Nosema.9 Vemuganti reported a case series of five patients of microsporidial stromal keratitis from South India.10 The keratoconjunctivitis form of the disease has been reported in both the seronegative HIV patients and healthy individuals.11,12 Currently microsporidia are recognized as an opportunistic infection in the immunocompromised patients. The source of infection is thought to be either orofaecal, resulting from direct inoculation, or occurring after trauma.5 Direct inoculation may occur with close contacts representing spread from other infected persons13,14 or following contact with domestic animals such as cats and birds.9,15 The normal life cycle of microsporidia comprises of invasion of the spore into the human host cell followed by discharge of the contents into the cytoplasm .Within the cell the sporoblast divides by binary fission to form scizont with 2–6 nuclei, which split into unicellular meronts .The meronts
Figure 1. (A) The clinical appearance or the right eye corneal abcess in case 1; (B) The appearance of typical microsporidia. (Acid fast stain, original magnification x1000); (C and D) Transmission electron microscopy of microsporidia in the same case (Original magnification x12 K).
201
Microsporidial keratitis: Literature review and report of 2 cases
Figure 2. (A) Histopathology of the acute stromal keratitis in case 2 (Hematoxylin and eosin, original magnification x100); (B) Similar appearance of microsporidia organisms within the stroma (Acid fast stain, original magnification x1000); (C) Transmission electron microscopy of structures resembling microsporida (Original magnification x8000); (D) The clinical appearance of the right eye with a failed corneal graft after 1 year.
then secrete a rigid capsule and the fully formed spore measures about 2.5 1.5 microns. The cell eventually ruptures to continue the cycle and further destruction of the host tissue.16
Microbiology facts In infectious diseases, the isolation techniques and identification tools provide rapid determination of the causative organism, the problem with microsporidia is that they are obligate intracellular parasites requiring cell culture systems for growth. Therefore, the diagnosis mainly depends on morphological demonstration of the organisms themselves in scrapings or tissues. Microsporidia are small (3.5–5.0 lm by 2.0–3.0 lm), oval obligate intracellular eukaryotic protozoan parasites that belong to phylum Microspora. More than 100 species have been classified into approximately 100 genera, and about 13 species have been reported to infect mammals.4,13–15 Phylogenetically microsporidia are early eukaryotic organisms because they have a true nucleus, possess prokaryotic like ribosome and lack mitochondria. 14 Joseph reviewed the disease and named four genera that infect humans Encephalitozoon, Nosema, Pleistophora and Enterocytozoon.6 Other reports showed that seven genera (Enterocytozoon species, Brachiola species, Encephalitozoon species, Pleistophora species, Nosema species, Vittaforma species and Trachipleistophora species) as well as unclassified microsporidia (collectively referred to as Microsporidium) have been associated with human disease involving immunocompromised patients.4,13–15 Microsporidia have developed a specific process to infect their host which takes place in vitro.17 It involves spore activation and polar tube discharge, by which the infective sporoplasm is injected into the host cell cytoplasm.18 It is followed by immediate breakdown of sporoplasm compartmentalization, producing an increase in osmotic pressure
which triggers polar tube eversion and injection of the sporoplasm into the host cell.18
Clinical features Ocular features of this type of infection can either represent corneal stromal keratitis which mainly affects immunocompetent patients and is commonly caused by Nosema corneum4 or superficial punctuate keratoconjunctivitis which usually affects acquired immune deficiency syndrome (AIDS) patients or contact lens wearers, in which cases are mostly caused by genus Encephalitozoon. Keratoconjuctivitis may also affect immunocompetent humans. Microsporidial keratitis in healthy persons can mimic herpetic keratitis with history of recurrent redness, pain, photophobia, watering, and decreased vision. Such cases may be mistaken and treated with antiviral and topical steroids which were documented in the management history of our first case. The clinical findings include lid edema, congested conjunctiva and corneal lesions. The corneal involvement is usually in the form of mid to deep stromal infiltrates surrounded by edema with either intact epithelium and/or epithelial defect over the stromal lesions. The endothelium does not show precipitates.
Diagnosis Microsporidia are small, obligate intracellular parasites that produce infective spores. They are fastidious organisms that are difficult to culture. The organism can be isolated using special tissue culture techniques, which are available only in few specialized laboratories, and hence routine microbiological diagnosis might be difficult.19,20 Alcohol-fixed cytologic samples of scrapings from the conjunctiva, corneal epithelium, or both as well as biopsy specimens are proven to be very useful for demonstrating microsporidial blastospores.8,21
202 The light microscopy has greatly improved lately in diagnosing microsporidiosis. Conjunctival scrapings alone can provide a satisfactory specimen for cytologic diagnosis in microsporidial epithelial punctuate keratoconjunctivitis. Cytologic findings demonstrate small, oval organisms within the epithelial cells, stromal keratocytes, and histiocytes as well as free extracellular structures.22–24 These spores have uniform oval shape and are non-budding, which helps to differentiate them from bacteria and yeasts.25 The spores stain strongly with gram stain.26,27 Giemsa and 1% acid fast stains have also been successfully used to demonstrate microsporidial spores.22,23 Occasionally, these spores stain poorly or not at all with routine stains (hematoxylin/eosin or the Papanicolaou methods), with the organism being easily overlooked in biopsy specimens or cytologic preparations.25,28 Definitive diagnosis and species differentiation may necessitate EM studies. This has been used for ocular infections by examination of tissue biopsy from cornea or conjunctiva using electron microscope to demonstrate the number of coils of the filament.22–24,26–28To differentiate between Nosema species and Encephalitozoon several electron microscopic features can be identified. In Nosema the coils of the filament range from 11 to 13 in Nosema versus 4–7 in Encephalitozoon. The Nosmea are larger than Encephalitozoon; also the absence of a parasitophorous vacuole surrounding the organism within the host cell is more consistent with Nosema.16 Immuno-fluorescent staining techniques are advanced tools which need specific antibodies only available in research laboratories. This was performed for our first case for identification of the organism which belongs to Encephalitozoon species. In the last few years, the use of molecular techniques has been developed for the detection and species differentiation of microsporidia.
H.M. Alkatan et al. Secondary infection and penetration of the organisms into the deeper stroma may follow corneal scrapings, use of topical steroids or bandage contact lenses.23 In case where the medical treatment fails PKP has been recommended rather than lamellar graft to treat deep stromal microsporidiosis to avoid any chance of recurrence in the lamellar bed.10 However, deep anterior lamellar keratoplasty has been also recently considered as an option for visual rehabilitation.39
Conclusion Microsporidia are an important cause of disease in both HIV and non-HIV patients with or without immunosuppression. High index of suspicion is needed for prompt diagnosis and treatment. Therefore, ophthalmologists should consider microsporidia in the differential diagnosis of infectious keratitis.40 As diagnosis by conventional methods is still challenging and may need an advanced laboratory tools such as EM, newer methods such as molecular biology (PCR) or serology methods should be developed to be utilized for the diagnosis and species differentiation of microsporidia which may have important implication in the management. Being uncommon or being overlooked again necessitates careful study of this organism and its microbiological behavior. This also makes the judgment on current therapeutics incomplete. Many treatment modalities for ocular microsporidiosis have been suggested in the literature including scraping, bandage contact lenses, steroids, and antimicrobial agents with successful outcome in selected cases. Fumagillin has shown to be an effective medical treatment while PKP is the preferred alternative surgical management.
Treatment
Acknowledgment
So far there is no known definitive medical treatment of deep microsporidial corneal stromal infections. Some previous reports have suggested that treatment with topical propamidine isethionate 0.1% (Brolene)28,29or systemic itraconazole19 which might be effective against microsporidial superficial keratoconjuctivitis. Subjective improvement was reported with debulking and a combination of topical neomycin, polymyxin B and bacitracin antibiotics in a patient with bilateral epithelial keratopathy caused by Encephalitozoon; while complete resolution was achieved only after administration of oral itraconazole.22 Successful treatment of microsporidial superficial keratoconjuctivitis with topical fumagillin has been also reported.30–35 Fumagillin is a naturally secreted water-insoluble antibiotic of Aspergillus fumigatus and is noted to possess an inhibitory effect on some intestinal protozoa.34 Fumagillin bicyclohexylammonium salt is the water soluble form of fumagillin used commercially. The mechanism of action of fumagillin is not clearly understood but it may alter DNA content or inhibit RNA synthesis in the organism.36,37 Some authors have also suggested the role of oral albendazole in combination with topical fumagillin. Others have shown good response to medical treatment with systemic albendazole and topical chlorhexidine in a selected case where the infection is limited to the mid-stroma.38
This project is approved by the institutional review board (IRB) and human ethics committee (HEC) at KKESH.
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