The myopathology of the Prune Belly Syndrome

153

Journal of the neurological Sciences Elsevier Publishing Company, Amsterdam - Printed in The Netherlands

The Myopathology of the Prune Belly Syndrome A. K. AFIFI, J. REBEIZ, J. MIRE, S. J. A N D O N I A N AND V. M. DER KALOUSTIAN Departments of Human Morphology, Pathology and Pediatrics, School of Medicine, American University of Beirut, Beirut (Lebanon) (Received 28 May, 1971)

INTRODUCTION

The "Prune Belly Syndrome" or "Triad Syndrome" is a well-established but rare entity. It is characterized by absence of normal abdominal musculature, mega-ureter and undescended testicles. Other associated anomalies include malrotation of the midgut, chest wall deformities, anomalies of the lower extremities, cardiac anomalies, poly- and syndactyly, congenital dislocation of the hip, spina bifida, meningomyelocele, omphalocele, eye and ear anomalies, choanal atresia and micrognathia (Silverman and Huang 1950; Lattimer 1953; Mathieu, Goldowsky, Chaset and Mathieu 1953; Brierre 1963; Burke, Shin and Kelalis 1969). The syndrome was first described by Parker (1895). Since then, a total of 190 cases have been reported ; all except 10 were males. While most reports dealt with urogenital anomalies in this disorder, very few studies of the muscular abnormality are available and none describes the ultrastructural appearance of skeletal musculature in this syndrome. It is for this reason that we report the light and electron microscopic myopathology in a female with the Prune Belly syndrome. CLINICAL DATA

N.K., an 8-month-old female, was noted at birth to have symmetrical swelling of both sides of the abdomen accentuated by cough or crying. The parents are first cousins. A female and male siblings died of unknown causes at the age of 16 years and 2 months respectively. At the age of 6 months, the girl had pneumonia which was treated with penicillin and cough syrup. She however continued to have a chronic cough with intermittent fever for which she was admitted to the American University of Beirut Medical Center. This investigation was supported by the Lebanese National Council for Scientific Research Grant No. 38-5757, Grant No. 18-5150 from the Medical Research Committee, American University of Beirut and Grant No. 38-5755 from the Muscular Dystrophy Association of Great Britain.

J. neurol. Sci., 1972, 15:153-165

154

A. K. AFIFI, J. REBEIZ, J. MIRE, S. J. ANDONIAN, V. M. DER KALOUSTIAN

Physical examination revealed an underdeveloped (length 67 cm, weight 6.5 kg) but alert and active baby girl. The abdominal wall was very lax and bulged laterally on both sides (Fig. 1). The abdominal viscera were easily palpable beneath a thin abdominal wall.

Fig. 1. A photograph of the patient showing 'bulging of the abdomen.

Laboratory studies revealed the following: haemoglobin 9.9 g/100 ml. Bone marrow aspirate was compatible with mild iron deficiency anaemia. Serum iron was 76 mg/100 ml and iron-binding capacity was 416 mg/100 ml with 15.4 ~ saturation. Creatine kinase (CK), serum glutamic oxaloacetic transaminase (SGOT), serum glutamic pyruvic transaminase (SGPT), total serum protein, albumin-globulin ratio and serum immunoelectrophoresis were normal. Urinalysis was repeatedly normal. Intravenous pyelography, voiding cystography, barium meal and follow-through and barium enema were all normal. Chest X-ray revealed a persistent air bronchogram from collapse of the left lower lobe. Electromyography of the anterior tibial, gastrocnemius, vastus lateralis and brachioradialis muscles and the thin strip of rectus abdominis adjacent to the midline was normal. METHODS

Muscle biopsy obtained from the rectus abdominis was studied by light and electron microscopy. A part of the biopsy was fixed in 10 ~ formol saline and embedded in paraffin for light microscopic study. 10 # sections were stained with haematoxylin and eosin (HE), Van Gieson and phosphotungstic acid-haematoxylin (PTAH). Material for high-resolution light microscopy and electron microscopy was fixed stretched in 3 ~ glutaraldehyde in phosphate (Millonig) buffer at pH 7.4 for 1 hr, post-fixed in 1 ~ buffered osmium tetroxide for 1 hr, dehydrated in graded alcohol and embedded in Epon 812. 1 gm thin sections were stained with a periodic acid-Schiff's reagent-PTAH (PAS-PTAH) method modified for semithin Epon-embedded sections. 600 A thick sections cut on an LKB III ultratome using a glass or diamond knife were stained with uranyl acetate and lead citrate (Reynolds) and studied using an RCA-EMU-4 electron microscope at 50 kV. J. neurol. Sci.+ 1972, 15" 153-165

MYOPATHOLOGY OF THE PRUNE BELLY SYNDROME

155

Fig. 2. Photomicrograph showing light microscopic myopathology. A : increased number of nuclei and their circular arrangement. B: a capillary (arrow) within a muscle fibre. C: muscle fibres with central nuclei (arrow) embedded in massive collagen (Co). D : a giant muscle fibre adjacent to a normal fibre. E : muscle fibres (star) embedded in massive collagen (Co). Giant fibres, normal fibres and atrophic fibres are intermixed. F: a necrotic fibre invaded by macrophages. HE, 10/~m. A, x 1600; B, x 1200; C, x 400; D,'x 1500;E, x 100;F, × 1300.

J. neurol. Sci.,1972,15:153-165

156

A. K. AFIFI, J. REBEIZ, J. MIRE, S. J. ANDONIAN. V. M. DER KAI,OUSI'IAN

Fig. 3. Electron micrograph showing varying degrees of Z-line changes. Minor alterations (arrow), extensive alterations (double arrows). S, sarcolemma; Co, collagen invasion of basement membrane. × 15,200. RESULTS

Conventional light microscopy (Fig. 2) Eighty-three consecutive and gapless sections were examined. The variation in J. neuroI. Sci.,1972,15:153 165

MYOPATHOLOGY OF THE PRUNE BELLY SYNDROME

157

Fig. 4. Electron micrograph showing A and I bands (A, I) and no Z-line. × 20,000.

muscle fibre diameter was very striking. Some fibres were reduced to a few micra in diameter, while others had a diameter of over 120 #m. The atrophic and hypertrophic fibres were distributed haphazardly and most of the small fibres were embedded in dense endomysial connective tissue. M a n y of the large and some of the small fibres exhibited the most unusual sarcolemmal nuclear abnormality. In addition to a definite increase in the absolute n u m b e r of sarcolemmal nuclei, which in some fibres exceeded J. neurol. Sci., 1972, 15:153-165

158

A. K. AFIFI, J. REBEIZ, J. MIRE, S. J. ANDONIAN, V. M. DER KALOUSI'IAN

Fig. 5. Electron micrograph showing waviness and disorganization of myofilaments (arrow) and fragmentation of Z-line (double arrow). MF, myofibril. A, × 34,800: B. x 10,01X~.

20 nuclei in each 10 #m transverse section, many of these nuclei were orientated in practically all directions. Often, these nuclei were orientated along the transverse diameter of the fibre and occasionally in a circular pattern sandwiched between an inner circular core of sarcoplasm and an outer concentric circular core. Many such hypernucleated fibres had a sarcoplasm-free zone. Splitting of these fibres into two or J. neurol. Sci.,1972.15:153

165

MYOPATHOI-DGY OF THE PRUNE BELLY SYNDROME

159

Fig. 6. Electron micrograph showing loss of myofilaments and replacement with mitochondria (Mi) and glycogen (G). MF, myofibril ; Z, Z-line. x 41,400

more smaller ones, took place along the plane of this sarcoplasm-free zone or along the plane of the centrally-placed nuclei. Occasionally numerous nuclei were clumped together within one fibre. Segmental muscle fibre necrosis with phagocytosis and basophilia of the degenerated sarcoplasm was of frequent occurrence. However, nowhere in the sections was there any evidence of any regenerative activity or of any J. neurol. Sci., 1972, 15:153-165

160

A . K . AFIFI, J. REBEIZ, J. MIRE, S. J. ANI)ONIAN. V. M. I)ER KALO[ SIIAN

Fig. 7. Electron micrograph showing a ghost fibre (F) embedded in collagen (Co)i < 25.001)

inflammatory process. In two fibres small capillaries containing red and white blot~d cells were seen in more than 15 consecutive serial sections.

Electron microscopy M a n y muscle fibres retained their normal ultrastructural appearance. Others showed abnormalities in the Z-line, myofilaments, sarcolemma, sarcoplasmic J. neurol. Sci., 19"/2, 15:153 165

MYOPATHOLOGY OF THE PRUNE BELLY SYNDROME

161

Fig. 8. Electron micrograph showing dilation of sarcoplasmic reticulum profiles (SR) in subsarcolemmal sites (A) and within the fibre (B). Arrow in A points to an inclusion within a mitochondrion. Mi, mitochondria. A, x 20,000; B, x 46,400.

reticulum and collagen. The sarcolemma was thrown into many finger-like projections containing contractile elements. The most striking abnormality involved Zlines and myofilaments. Z-line changes varied from minor local fragmentation or streaming to an extensive disorganization of Z-line structure throughout the muscle ,I. neurol. Sci., 1972, 15:153-165

162

A. K. AFIFI, J. REBEIZ, J. MIRE, S. J. ANDONIAN, V. M. DER KALOUS'I-IAN

fibre. The latter included widening and streaming of the Z-line across one or mc~rc sarcomere in multiple sites within the fibre (Fig. 3). In some fibres, the Z-line was lost (Fig. 4). In such fibres, the thick filaments showed interrupted areas of segmental thickenings (Fig. 5). Myofilaments in affected fibres lost their linear pattern and exhibited varying degrees of scattering and waviness (Fig. 5). In many areas myofilaments were lost and their place was filled with filamentous debris, glycogen, sarcoplasmic reticulum profiles and aggregates of mitochondria (Fig. 6). Severely atrophic fibres were composed of a sarcolemmal lining and myofilamentous debris (Fig. 7). Conspicuous dilatations of sarcoplasmic reticulum profiles were seen particularly in subsarcolemmal sites but also deep within the fibre (Fig. 8). Excessive amounts of collagen fibres were seen. Many of these collagen fibres were in close proximity to or attached to the basement membrane of muscle fibres (Fig. 3). DISCUSSION

The triad of aplasia or hypoplasia of abdominal muscles, megaureter and undescended testicles described in the typical Prune Belly syndrome is not present in all cases. The classical picture may be absent especially in female patients (Burke et al. 1969). Thus the syndrome presents a spectrum ranging from the severe cases with multiple system involvement to the mild case where muscle pathology is the main finding. Being a female, our patient had the mild form of the disease and presented mainly with hypoplasia of the abdominal muscles. The involvement of muscle in the Prune Belly syndrome varies from partial hypoplasia to complete absence of abdominal musculature. Partial hypoplasia may be so mild as to pass unrecognized. The involvement of abdominal muscles may be generalized, more pronounced in the lower abdominal muscles or may be limited to one side of the abdomen (Nunn and Stephens 1961). The abdominal muscles may be thin but arranged in correct layers, or only one layer may be present (Nunn and Stephens 1961). Skeletal muscles elsewhere are usually unaffected (Burkholder, Harper and Beach 1970). There is uniformity in reported cases on the impressive increase of fibrous tissue in involved muscles. In one report (O'Kell 1969) myotubular fibres are found. Our light microscopic findings confirm those already described in the literature. No myotubes were seen in our material. The variation in fibre size, the presence of giant fibres, of central nuclei and increased fibrous tissue are similar to the changes seen in muscular dystrophy. No ultrastructural observations on the myopathology of this syndrome are available in the literature. The Z-line abnormality resembles that seen in central core disease (Seitelberger, Wanko and Gavin 1961 ; Shy, Engel and Wanko 1962 ; Afifi, Smith and Zellweger 1965; Gonatas, Perez, Shy and Evangelista 1965). Z-line abnormality in the latter condition, however, is limited to the core of the fibre, is of greater magnitude and is usually associated with a decrease or absence of mitochondria and sarcoplasmic reticulum profiles. In contrast, Z-line irregularity inthe Prune Belly syndrome is not limited to the centre of the fibre, having been observed close to the sarcolemma as well as adjacent to central nuclei. Absence of the Z-line J. neurol. Sci.,1972,15:153-..165

MYOPATHOLOGY OF THE PRUNE BELLY SYNDROME

163

has been reported in some cases of central core disease, and was seen in some fibres in our material. Similar but less extensive Z-line changes have been described in muscular dystrophy carriers (Milhorat, Shafiq and Goldstone 1966) and in the PraderWilli syndrome (Afifi and Zellweger 1969). The myofilamentous disarray and loss seen in a number of fibres in our case is not unique to this condition, having been reported as a late stage of muscle damage in a variety of neuromuscular disorders. Myofilaments are delicate structures highly vulnerable to injury and respond uniformly to different types of insults of varying cause. The segmental thickening of thick filaments has been observed in colchicineinduced myopathy (Markand and D'Agostino 1971). The sarcolemmal outpouchings probably represent exaggerated normal folds. Similar tubular invaginations have been described in normal muscle and some penetrate deep into the fibre (Porter and Franzini-Armstrong 1965). They superficially resemble sarcolemmal indentations reported in denervated muscle (Pellegrino and Franzini 1963; Afifi, Aleu, Goodgold and Mackay 1966). The latter, however, are devoid of contractile material. The increase in mitochondria in sites of myofilamentous loss may be an attempt at repair. Similar alterations have been observed in early stages of cortisone-induced myopathy (Afifi and Bergman 1969) and in moderately-affected fibres in congenital muscular dystrophy (Afifi, Zellweger, McCormick and Mergner 1969) suggesting a possible role of this organelle in the response of fibres to injury. Mitochondrial hyperplasia is usually associated with increased metabolic activity (Luft, Ikkos, Palmieri, Ernster and Afzelius 1962). Dilatation of the sarcotubular system occurred in relatively intact regions of the fibre and involved the longitudinal component of the system which is concerned with metabolic function. Similar changes have been described in congenital muscular dystrophy (Pearce 1963 ; Gubbay, Walton and Pearce 1966 ; Afifi et al. 1969) and in early stages of other types of dystrophy (Van Breemen 1960; Pearce 1963) but are probably non-specific. The marked increase in collagen in this disorder is out of proportion to the degree of involvement of the contractile apparatus. It thus resembles that seen in congenital muscular dystrophy (Pearce 1963, 1965 ; Gubbay et al. 1966 ; Afifi et al. 1969). As in congenital muscular dystrophy, collagen in this material was fused with the surface of the muscle fibre without invading any other component of the fibre. A major problem in the Prune Belly syndrome is the aetiology of the muscular abnormalities. Two hypotheses are usually cited. The first purports to show that the hypoplasia or aplasia of abdominal musculature is a manifestation of pressure atrophy caused by prolonged and marked distension of the urinary bladder (Housden 1934). Abdominal muscles are laid down about the fifth week of embryonic life, and excretion of urine begins at about the ninth week. This hypothesis fails to account for cases in which muscular hypoplasia occurs with absent or only mild urinary tract obstruction. Nunn and Stephens (1961), on the other hand, propose an arrest of development as the basis for the muscular hypoplasia. They suggest that, at a certain stage of development, stimuli might result in imperfect muscularization and growth of the abdominal J. neurol. Sci., 1972, 15:153-165

164

A. K. AFIFI, J. REBEIZ, J. MIRE, S. J. ANDONIAN, V. M. DER KALOUSTIAN

wall. The finding of myotubes in the case reported by O'Kell (1969) gives credence t~> this hypothesis. The findings in our case and those in the literature are however ~lt variance with O'Kell's observation. No myotubes were seen in our case or in most of those reported in the literature. Our light microscopic findings give ample evidence of an active disease process characterized by segmental muscle fibre necrosis without regeneration. This finding in our opinion rules out both hypotheses. The absence of reports of such an active disease process in the literature may reflect the time at which the muscle was sampled, for the end-stage picture of a necrotizing myopathy is the overgrowth of dense collagenous tissue with or without lipomatosis. Purely "myopathic" changes have been described in neurogenic atrophy (Drachman, Murphy, Nigam and Hills 1967); however, it is most unlikely that we are dealing with a neuropathy or a restricted motor neurone disease for in such entities muscle regeneration is usually seen. For the same reason aplasia of part or all the motor neurons or the thoracolumbar spinal segments is unlikely. Our electron microscopic observations are of nonspecific nature and point to some similarities between the" cytological alterations seen in muscle in the Prune Belly syndrome, in central core disease and congenital muscular dystrophy. Thus the light microscopic findings and the multifaceted involvement of muscle organelles, of the contractile apparatus and collagen are best explained by an active myopathic process rather than on the basis of developmental arrest or a passive pressure effect. It is likely therefore that a genetically-determined congenital type of myopathy is the basis of the myopathology in this syndrome. Restricted myopathies such as ocular and oculopharyngeal myopathies do occur, and the Prune Belly syndrome in our opinion may represent yet another type of restricted myopathy. Obviously a greater insight into the myopathology of this syndrome will be forthcoming when complete post-mortem examinations of such cases are available. SUMMARY

The Prune Belly Syndrome or Triad Syndrome is a rare disorder characterized by hypoplasia or aplasia of abdominal musculature, urogenital anomalies and undescended testicles. The majority of the reported cases are males. A female case of the mild variant of this syndrome is presented. The light and electron microscopic changes in the voluntary muscles are described. They consisted of variations in fibre size, fibre necrosis, an increase in sarcolemmal nuclei, the presence of capillaries within muscle fibres, excessive collagen accumulation, Z-line abnormalities, sarcoptasmic reticulum dilatation and myofilamentous disarray and loss. We propose the hypothesis that a genetically-determined or congenital type of myopathy may be the basis of this syndrome. REFERENCES AFIFI, A. K. AND R. BERGMAN (1969) Steroid myopathy. A study of the evolution of the muscle lesion in rabbits, Johns Hopk. reed. J., 124: 66--86. AHFI, A. K. AND H. ZELLWEGER (1969) Pathology of muscular hypotonia in the Prader Willi syndrome.

J. neuroI. Sci.,1972,15:153-165

MYOPATHOLOGY OF THE PRUNE BELLY SYNDROME

165

Light and electron microscopic study, J. neurol. Sci., 9: 49~51. AHEI, A. K., J. W. SMITHAND H. ZELLWEGER(1965) Congenital nonprogressive myopathy: central core disease and nemaline myopathy in one family, Neurology (Minneap.), 15: 371-381. AFIEI, A. K., F. P. ALLY, J. GOODGOLD ANt) B. MACKAY (1966) Ultrastructure of atrophic muscle in amyotrophic lateral sclerosis, Neurology (Minneap,), 16: 475-481. AFIFI, A. K., H. ZELLW~GER,W. F. McCoRMICK AND W. MERGNER(1969) Congenital muscular dystrophy: Light and electron microscopic observations, J. Neurol. Neurosuro. Psychiat., 32: 273-280. BRIERRE, J. (1963). Congenital abnormalities of the genitourinary tract: Abdominal muscle dysplasia and choanal atresia, Pediatrics, 31 : 290-296. BURKE, E. C., M. H. SHIN AND P. P. KELALIS (1969) Prune Belly Syndrome. Clinical findings and survival, Amer. J. Dis. Childh., ll7: 668~571. BURKHOLDER,G. V., R. C. HARPERAND P. D. BEACH(1970) Congenital absence of the abdominal muscles: A clinicopathologic correlation, Amer. J. clin. Path., 53: 602-608. DRACHMAN, D. B., S. R. MURPHY, M. P. NIGAMAND J. R. HILLS (1967) Myopathic changes in chronically denervated muscle, Arch. Neurol. (Chic.), 16: 14-24. GONATAS, N. K., M. C. PEREZ, G. M. SHY ANt) 1. EVANGELISTA(1965) Central "core" disease of skeletal muscle, ultrastructural and cytochemical observations in two cases, Amer. J. Path., 47: 503-524. GUBBAY, S. S., J. N. WALTONAND G. W. PEARCE(1966) Clinical and pathological study of a case of congenital muscular dystrophy, J. Neurol. Neurosurg. Psychiat., 29: 500-508. HOUSDEN, L. G. (1934) Congenital absence of abdominal muscles, Arch. Dis. Childh., 9: 219. LATTIMER, J. K. (1953) Congenital deficiency of the abdominal musculature and associated genitourinary anomalies: A report of 22 cases, J. UroL (Baltimore), 79: 343-352. LUFT, R., D. IKKOS, G. PALMIERI,L. ERNSTERAND B. AFZELIUS(1962) A case of severe hypermetabolism of nonthyroid origin with a defect in the maintenance of mitochondrial respiratory control: a correlated clinical, biochemical and morphological study, J. clin. Invest., 41 : 1776-1804. MARKAND, O. N. AND A. N. D'AGOSTINO (1971) Ultrastructural changes in skeletal muscle induced by colchicine, Arch. Neurol. (Chic.), 24: 72-82. MATHIEU, B. J., S. GOLDOWSKY,N. CHASETAND P. C. MATHIEU (1953) Congenital deficiency of the abdominal muscles (with associated multiple anomalies), J. Pediat., 42: 92-98. MILHORAT, A. T., S. A. SHAFIQ AND L. GOLDSTONE (1966) Changes in muscle structure in dystrophic patients, carriers and normal siblings seen by electron microscopy; correlation with levels of serum creatinephosphokinase, Ann. N.Y. A cad. Sci., 138: 246-292. NUNN, I. N. AND F. I3. STEPHENS (1961) The triad syndrome: a composite anomaly of the abdominal wall, urinary system and testes, J. Urol. (Baltimore), 86: 782-794. O'KELL, R. T. (1969) Embryonic abdominal musculature associated with anomalies of the genitourinary and gastrointestinal systems, Amer. J. Obstet. Gynec., 105: 1283-1284. PARKER, R. W., (1895) Absence of abdominal muscles in an infant, Lancet, i: 1252. PEARCE, G. W. (1963) Electron microscopy in the study of muscular dystrophy. In: G. H. BOURNEAND M. N. GOLARZ (Eds.), Muscular Dystrophy in Man and Animals, Karger, Basle, pp. 160-177. PEARCE, G. W. (1965) The sarcolemma and sarcotubular systems in normal and dystrophic muscle. In: MEMBERSOF THE RESEARCH COMMITTEEOF THE MUSCULAR DYSTROPHY GROUP, Research in Muscular Dystrophy (Proceedings of the 3rd Symposium), Lippincott, Philadelphia, Penn., 1965, pp. 146-156. PELLEGRINO, G. AND C. FRANZINI (1963) An electron microscopic study of denervation atrophy in red and white skeletal muscle fibers, J. Cell Biol., 17: 327-349. PORTER, K. R. AND C. FRANZINI-ARMSTRONG0965) The sarcoplasmic reticulum. Sci. Amer., 212: 73-80. SEITELBERGER,F., Z. WANKO AND M. A. GAVIN (1961) The muscle fiber in central core disease, histochemical and electron microscopic observations, Acta neuropath. (Berl.), 1 : 223-237. SHY, G. M., W. K. ENGELAND T. WANKO (1962) Central core disease: a myofibrillary and mitochondrial abnormality of muscle, Ann. intern. Med., 56:511-520. SILVERMAN,F. N. AND N. HUANG (1950) Congenital absence of the abdominal muscles associated with malformation of the genitourinary and alimentary tracts: report of cases and review of literature, Amer. J. Dis. Childh., 80: 91-124. VAN BREEMEN,V. L. (1960) Ultrastructure of human muscle, Part 2 (Observations on dystrophic striated muscle fibres), Amer. J. Path., 37: 333-341.

J. neurol. Sci., 1972, 15:153-165