Cytoplasmic body neuromyopathy presenting as respiratory failure and weight loss

Titin founder mutation is a common cause of myofibrillar myopathy with early respiratory failure

OBJECTIVE

Titin gene (TTN) mutations have been described in eight families with hereditary myopathy with early respiratory failure (HMERF). Some of the original patients had features resembling myofibrillar myopathy (MFM), arguing that TTN mutations could be a much more common cause of inherited muscle disease, especially in presence of early respiratory involvement.

METHODS

We studied 127 undiagnosed patients with clinical presentation compatible with MFM. Sanger sequencing for the two previously described TTN mutations in HMERF (p.C30071R in the 119th fibronectin-3 (FN3) domain, and p.R32450W in the kinase domain) was performed in all patients. Patients with mutations had detailed review of their clinical records, muscle MRI findings and muscle pathology.

RESULTS

We identified five new families with the p.C30071R mutation who were clinically similar to previously reported cases, and muscle pathology demonstrated diagnostic features of MFM. Two further families had novel variants in the 119th FN3 domain (p.P30091L and p.N30145K). No patients were identified with mutations at position p.32450.

CONCLUSIONS

Mutations in TTN are a cause of MFM, and titinopathy is more common than previously thought. The finding of the p.C30071R mutation in 3.9% of our study population is likely due to a British founder effect. The occurrence of novel FN3 domain variants, although still of uncertain pathogenicity, suggests that other mutations in this domain may cause MFM, and that the disease is likely to be globally distributed. We suggest that HMERF due to mutations in the TTN gene be nosologically classified as MFM-titinopathy.

Titin mutation segregates with hereditary myopathy with early respiratory failure

In 2001, we described an autosomal dominant myopathy characterized by neuromuscular ventilatory failure in ambulant patients. Here we describe the underlying genetic basis for the disorder, and we define the neuromuscular, respiratory and radiological phenotype in a study of 31 mutation carriers followed for up to 31 years. A combination of genome-wide linkage and whole exome sequencing revealed the likely causal genetic variant in the titin (TTN) gene (g.274375T>C; p.Cys30071Arg) within a shared haplotype of 2.93 Mbp on chromosome 2. This segregated with the phenotype in 21 individuals from the original family, nine subjects in a second family with the same highly selective pattern of muscle involvement on magnetic resonance imaging and a third familial case with a similar phenotype. Comparing the mutation carriers revealed novel features not apparent in our original report. The clinical presentation included predominant distal, proximal or respiratory muscle weakness. The age of onset was highly variable, from early adulthood, and including a mild phenotype in advanced age. Muscle weakness was earlier onset and more severe in the lower extremities in nearly all patients. Seven patients also had axial muscle weakness. Respiratory function studies demonstrated a gradual deterioration over time, reflecting the progressive nature of this condition. Cardiomyopathy was not present in any of our patients despite up to 31 years of follow-up. Magnetic resonance muscle imaging was performed in 21 affected patients and revealed characteristic abnormalities with semitendinosus involvement in 20 of 21 patients studied, including 3 patients who were presymptomatic. Diagnostic muscle histopathology most frequently revealed eosinophilic inclusions (inclusion bodies) and rimmed vacuoles, but was non-specific in a minority of patients. These findings have important clinical implications. This disease should be considered in patients with adult-onset proximal or distal myopathy and early respiratory failure, even in the presence of non-specific muscle pathology. Muscle magnetic resonance imaging findings are characteristic and should be considered as an initial investigation, and if positive should prompt screening for mutations in TTN. With 363 exons, screening TTN presented a major challenge until recently. However, whole exome sequencing provides a reliable cost-effective approach, providing the gene of interest is adequately captured.

Hereditary myopathy with early respiratory failure associated with a mutation in A-band titin

Hereditary myopathy with early respiratory failure and extensive myofibrillar lesions has been described in sporadic and familial cases and linked to various chromosomal regions. The mutated gene is unknown in most cases. We studied eight individuals, from three apparently unrelated families, with clinical and pathological features of hereditary myopathy with early respiratory failure. The investigations included clinical examination, muscle histopathology and genetic analysis by whole exome sequencing and single nucleotide polymorphism arrays. All patients had adult onset muscle weakness in the pelvic girdle, neck flexors, respiratory and trunk muscles, and the majority had prominent calf hypertrophy. Examination of pulmonary function showed decreased vital capacity. No signs of cardiac muscle involvement were found. Muscle histopathological features included marked muscle fibre size variation, fibre splitting, numerous internal nuclei and fatty infiltration. Frequent groups of fibres showed eosinophilic inclusions and deposits. At the ultrastructural level, there were extensive myofibrillar lesions with marked Z-disc alterations. Whole exome sequencing in four individuals from one family revealed a missense mutation, g.274375T>C; p.Cys30071Arg, in the titin gene (TTN). The mutation, which changes a highly conserved residue in the myosin binding A-band titin, was demonstrated to segregate with the disease in all three families. High density single nucleotide polymorphism arrays covering the entire genome demonstrated sharing of a 6.99 Mb haplotype, located in chromosome region 2q31 including TTN, indicating common ancestry. Our results demonstrate a novel and the first disease-causing mutation in A-band titin associated with hereditary myopathy with early respiratory failure. The typical histopathological features with prominent myofibrillar lesions and inclusions in muscle and respiratory failure early in the clinical course should be incentives for analysis of TTN mutations.

An Italian case of hereditary myopathy with early respiratory failure (HMERF) not associated with the titin kinase domain R279W mutation

Hereditary myopathy with early respiratory failure (HMERF) is a rare disorder characterized by severe respiratory involvement at onset, muscle weakness starting in the early adulthood, and cytoplasmic bodies with peculiar immunohistochemical reactivity on muscle biopsy. Here we describe a patient who presented with hypercapnic coma at age 32. A detailed light and electron microscopy analysis on muscle biopsy was performed and, together with clinical data, led to the diagnosis. The R279W mutation in the TTN gene was excluded. This report expands the geographical region of incidence and encourages additional studies to clarify the genetic heterogeneity of the condition.

Cytoplasmic body myopathy masquerading as motor neuron disease

Cytoplasmic body myopathy (CBM) is characterized by proteinaceous inclusion bodies in muscle tissue. A 43-year-old woman presented with rapidly progressive weakness and dysphagia. Electromyography (EMG) elsewhere demonstrated lower-limb chronic partial denervation. Muscle biopsy showed fiber size variation without diagnostic features. A diagnosis of possible motor neuron disease was made and the patient was commenced on riluzole. Subsequently, the patient's condition stabilized, prompting reassessment. Repeat EMG demonstrated no features of denervation and was more suggestive of a myopathic process. Review of the original muscle biopsy showed cytoplasmic bodies. The case highlights a further diagnostic possibility in the assessment of patients with "possible" motor neuron disease. The clinical features of CBM are briefly reviewed.

Congenital myopathies at their molecular dawning

The introduction and application of molecular techniques have commenced to influence and alter the nosology of congenital myopathies. Long-known entities such as nemaline myopathies, core diseases, and desmin-related myopathies have now been found to be caused by unequivocal mutations. Several of these mutations and their genes have been identified by analyzing aggregates of proteins within muscle fibers as a morphological hallmark as in desminopathy and actinopathy, the latter a subtype among the nemaline myopathies. Immunohistochemistry has played a crucial role in recognizing this new group of protein aggregate myopathies within the spectrum of congenital myopathies. It is to be expected that other congenital myopathies marked by inclusion bodies may turn out to be such protein aggregate myopathies, depending on analysis of individual proteins within these protein aggregates and their association with putative gene mutations.

Co-existence of nemaline and cytoplasmic bodies in muscle of an infant with nemaline myopathy

A sporadic case of congenital myopathy had severe muscle weakness of neonatal onset. Nemaline and cytoplasmic bodies were detected in muscle biopsies taken at 4 months of age. These findings were consistent with a diagnosis of nemaline myopathy (severe neonatal form). The simultaneous and abundant presence of these two types of sarcoplasmic inclusion has been found in only a few cases. However, these cases suggest that the sarcoplasmic inclusions may be formed, at least partially, by common mechanisms.

Progress in desmin-related myopathies

Desmin-related myopathies are sporadic and familial neuromuscular conditions of considerable clinical heterogeneity uniformly marked by the pathologic accretion of desmin, often in a filamentous fashion. A large variety of other proteins, some of them cytoskeletal, also accrue. Morphologically, two types may be distinguished, one characterized by inclusions such as cytoplasmic and spheroid bodies or desmin-dystrophin plaques and another marked by granulofilamentous material. The genetic spectrum of desmin-related myopathies is quite diverse in that missense mutations and deletions in the desmin gene and a missense mutation in the alpha-B crystallin gene have been detected and several genes on other chromosomes have been mapped; the encoded protein products of these genes, however, are unknown. Accumulation of desmin and other proteins appears to be due to impaired nonlysosomal proteolysis. Mutant desmin that appears to be hyperphosphorylated seems to act as a seed protein for filament aggregation, inducing formation of inclusions and granulofilamentous material in these conditions. This condition is part of the group of disorders known as "surplus protein myopathies."

Familial cardiomyopathy and distal myopathy with abnormal desmin accumulation and migration

Desminopathies form a heterogeneous group of myopathies characterised by pathological aggregations of desmin. We report a family, where mother and daughter presented with an atrioventricular block and a slowly progressive distal muscular weakness, with non-homogeneous focal atrophy on computed tomography scans. The mother developed a severe global heart insufficiency necessitating a heart transplantation at 56 years of age. Skeletal muscle biopsies were characterised by inclusion bodies strongly expressing desmin and alpha B-crystallin, with a predominantly subsarcolemmal localisation. Ultrastructurally most inclusions corresponded to non-membrane bound granulo-filamentous material with disruption of myofibrils. An immunoblot showed a hyperintense desmin band at 53 kDa and a second band at 49 kDa, the latter being absent in controls. The cardiac muscle of the explanted heart showed very similar inclusions. These cases illustrate that in this distinct subtype of desminopathies the cardiac muscle alterations are comparable with those observed in skeletal muscle, and suggest the possibility of a primary desmin pathology.

Spheroid body myopathy revisited

Having reported spheroid body myopathy from Indiana (IN) inherited in an autosomal-dominant fashion several years ago, we now describe additional findings from the Oregon branch--briefly recorded earlier--and confirm earlier studies in another clinically affected IN member of this kinship demonstrating identical spheroid bodies within the myopathic muscle specimens. The spheroid bodies also contained increased amounts of desmin, alpha-B crystallin, and ubiquitin within muscle fibers. Our studies now have established that spheroid body myopathy is a member of the growing family of desminopathic neuromuscular conditions.

Desmin-related neuromuscular disorders

Desmin, the intermediate filament protein of skeletal muscle fibers, cardiac myocytes, and certain smooth muscle cells, is a member of the cytoskeleton linking Z-bands with the plasmalemma and the nucleus. The pathology of desmin in human neuromuscular disorders is always marked by increased amounts, diffusely or focally. Desmin is highly expressed in immature muscle fibers, both during fetal life and regeneration as well as in certain congenital myopathies, together with vimentin. Desmin is also enriched in neonatal myotonic dystrophy and small fibers in infantile spinal muscular atrophy. Focal accretion of desmin may be twofold, in conjunction with certain inclusion bodies, cytoplasmic and spheroid bodies, and in a more patchy fashion, granulofilamentous material. Both lesions have been found in certain families, affected by a myopathy and/or cardiomyopathy. Other proteins, e.g., dystrophin, vimentin, actin, ubiquitin, and alpha-B crystallin, may also be overexpressed. Desmin pathology may be genetically regulated or may merely reflect profoundly impaired metabolism of several proteins within myofibers.

Hereditary myopathy of the diaphragmatic muscles in Holstein-Friesian cattle

We describe a family line with an autosomal recessive disease of muscular dystrophy of the diaphragmatic muscles in Holstein-Friesian cattle. Histopathological examination in the present cases revealed various degenerative changes in the diaphragmatic and other thoracic muscles as follows: variation in muscle fiber diameter, fiber splitting, sarcoplasmic masses, ring fiber, vacuolar and hyalinized degeneration of muscle fibers. In addition, central core-like structures were the prominent features in the diaphragmatic muscles, occupying the center of the fiber or scattered within the fiber. These pathological alterations are consistent with the diaphragmatic myopathy previously reported in Meuse-Rhine-Yssel cattle in the Netherlands. The fibers containing core-like structures consisted of three distinct zones which could be well distinguished by NADH-tetrazolium reductase activity. This activity was absent in the innermost zone, decreased in the intermediate zone, and normal or increased in the periphery. Electron microscopically, this structure appeared to be composed of focal myofibrillar degeneration beginning with streaming or disintegration of the Z disk. We discuss here the similarity between this core-like structure and the other alternative organelles that have been reported previously, and a possible defect or storage in the cytoskeleton from the findings of the Z disk abnormalities.

Hereditary distal myopathy with granulo-filamentous cytoplasmic inclusions containing desmin, dystrophin and vimentin

A 56-year-old female and her 34-year-old daughter presented with a predominantly distal myopathy affecting the peroneal and calf muscles, neck flexors and hand muscles. Both patients and two other daughters had cardiac arrhythmias, three requiring the insertion of cardiac pacemakers. Skeletal muscle biopsies revealed a complex myopathic process with granular degeneration, rimmed vacuoles and eosinophilic cytoplasmic inclusions. Ultrastructurally, the inclusions were composed of electron dense granular material and filaments forming linear masses beneath the sarcolemma and rounded masses within the cytoplasm of the fibres. Immunohistochemistry revealed labelling of the inclusions for desmin, dystrophin and vimentin, but not for alpha-actinin, spectrin, utrophin or myosin heavy chains. This family shows a hereditary distal myopathy with some features in common with previously-reported cases in which biopsies showed cytoplasmic inclusion bodies containing desmin. This group of diseases is clinically and pathologically heterogeneous. In the present cases, the accumulation of cytoplasmic filaments may reflect a generalised disturbance of filamentous protein metabolism rather than a specific disorder of desmin.

Familial cardiomyopathy, mental retardation and myopathy associated with desmin-type intermediate filaments

The clinical and morphological findings of a familial case affected by mental retardation, severe biventricular hypertrophic cardiomyopathy and vacuolar myopathy are reported. The phenotype of this patient is similar to that described by other authors, in which a lysosomal glycogen storage disease with normal acid maltase levels was suspected. However, in our case the vacuoles were stained by several antibodies directed against various sarcolemmal proteins, such as dystrophin and spectrin, and therefore, were not of lysosomal origin. Some of these vacuoles were clearly derived from the splitting of the fibres and invagination of the extracellular space; autophagic vacuoles were not observed. The accumulation of desmin-type, intermediate filaments was demonstrated on immunocytochemistry both in the skeletal and cardiac muscles. A brother of the propositus was also affected by mental retardation, severe cardiomyopathy and died suddenly at the age of 24 yr. A cardiomyopathy and mental subnormality were also present in other male cousins of the proband, while sudden death occurred in several females relatives, whose intelligence was normal. None of these latter individuals was available for further investigation. This report expands the spectrum of desmin associated myopathy and cardiomyopathy to include a familial condition with associated mental retardation.

Desmin pathology in neuromuscular diseases

Desmin is an intermediate filament protein that in striated muscle is normally located at Z-bands, beneath the sarcolemma, and prominently at neuromuscular junctions. It is abundant during myogenesis and in regenerating fibers, but decreases in amount with maturation; in regenerating and denervated muscle fibers it is co-expressed with vimentin. Aggregates of desmin occur as nonspecific cytoplasmic bodies or cytoplasmic spheroid complexes, similar to the aggregates of keratin filaments in Mallory bodies or the neurofilament aggregates in Lewy bodies. In all three instances, alpha-B crystallin may be associated with desmin. There are now increasing numbers of neuromuscular disorders in which abnormal amounts of desmin, some abnormally phosphorylated, feature prominently in muscle fibres. Several of these diseases, including spheroid body myopathy, granulo-filamentous body myopathy and the dystrophinopathies, are familial. Ultrastructural and immunohistochemical studies of desmin have considerably broadened our understanding of the pathology of the cytoskeleton in muscle fibers and in certain hereditary neuromuscular diseases.

Inclusions in familial cytoplasmic body myopathy are stained by anti-dystrophin antibodies

We report here for the first time positive anti-dystrophin labelling of inclusions in three cases belonging to the same family affected by familial cytoplasmic body myopathy (CBM). Inclusions are also stained, as reported previously, by anti-actin antibodies. The anti-desmin reaction was negative in the centre of cytoplasmic bodies (CB) but showed an enhancement of staining in the peripheral part. Abnormal sarcoplasmic staining of fibres with CB was also observed with that antibody. Anti-vimentin antibody labelling was negative. At present, the significance of this labelling by anti-dystrophin antibodies is unknown, but will open new fields for further investigations in an attempt to understand CB pathogenesis.

Neuromyopathy and restrictive cardiomyopathy with accumulation of intermediate filaments: a clinical, morphological and biochemical study

The clinical, morphological and biochemical findings of a sporadic case, showing accumulation of desmin-type intermediate filaments in skeletal muscle and myocardium are described. Desmin storage was demonstrated by immunofluorescence, sodium dodecyl sulfate gel electrophoresis and two-dimensional gel electrophoresis. These findings are in agreement with those of Rappaport et al. (FEBS lett. 231:421-425, 1989). A sensory-motor polyneuropathy was established by electrophysiological studies and, ultrastructurally, intramuscular nerves showed accumulation of neurofilaments and neurotubules with formation of axonal spheroids. These findings are discussed considering all previous reports with related conditions.

Desmin and actin associated with cytoplasmic bodies in skeletal muscle fibers: immunocytochemical and fine structural studies, with a note on unusual 18- to 20-nm filaments

In a fine structural and immunocytochemical study, the latter performed on semithin sections of epoxy resin embedded skeletal muscle fibers, three types of cytoplasmic bodies were identified in a case of cytoplasmic body myopathy: (1) The first type, the classical type, showed a central core and a light halo with radiating actin filaments at the periphery. (2) The second type, the spheroid body was characterized by irregularly arranged granular masses associated with intermediate filaments. Desmin immunoreactivity occurred in the central and peripheral parts, where filaments of intermediate size were visualized by electron microscopy. Desmin immunoreactivity was noted also at the Z-bands of striated annulets, within areas of disordered myofibrils, such as sarcoplasmic masses, and in atrophic muscle fibers. (3) The third type of the cytoplasmic body was composed mainly of large masses of uneven granularity and electron density. The center of this type reacted to anti-actin antibody suggesting that the 5- to 6-nm filaments, which ultrastructurally proved to be a major component, were of the actin type. By contrast, neither intermediate filaments nor actin microfilaments were found by electron microscopy in cytoplasmic bodies in a second case where no immunoreaction to desmin or actin occurred. Anti-vimentin antibody stained only the cytoplasm of endomysial cells, but not the inclusion bodies. Some other, unusual inclusions with 18- to 20-nm tubulo-filamentous structures have to be distinguished from the various types of filaments in cytoplasmic bodies. It is concluded, that pleomorphism and heterogeneity of "cytoplasmic bodies" have to be taken into consideration when classifying cytoplasmic body myopathies.

Myopathy with respiratory failure and typical myofibrillar lesions

16 patients representing 7 different pedigrees exhibited an unusual, adult onset limb-girdle myopathy with typical clinical hallmarks. In a majority of cases there was evidence of an autosomal dominant inheritance. A prominent early finding in all cases was respiratory muscle weakness, and in many of these an acute respiratory incapacity was the reason for the first neurological examination. Neck flexor and sometimes foot extensor weakness were other early symptoms. The clinical picture seems to be at variance with that of the more well known hereditary myopathies. Electrophysiological analysis confirmed a myopathy and serum muscle enzyme concentrations were normal or slightly elevated. Muscle biopsy findings revealed myofibrillar changes which, at the light microscopy level, included plaques that stained strongly with rhodamine-conjugated phalloidin, a specific marker for F-actin. At the ultrastructural level, these plaques were observed to be composed of moderately dense, thin filaments and were related to splitting of Z-discs or formed extensions from Z-discs. We believe that the muscle biopsy changes revealed by cytochemical and ultrastructural observations indicate defective myofibrillogenesis, and the possibility of defective actin polymerization is discussed. A conclusive answer requires further immunocytochemical and immunoelectrophoretic studies and possibly the application of molecular genetics.

Involvement of respiratory muscles in cytoplasmic body myopathy--a pathology study

A muscle biopsy and autopsy study of a child who died at 14 months of respiratory failure is described. A diagnosis of infantile cytoplasmic body myopathy was made due to the high percentage of cytoplasmic bodies (CBs), particularly in respiratory muscles. No pathological abnormalities were found in the central nervous system, peripheral nerves or visceral organs. Immunohistochemical studies suggested that the central core of CBs was stained for fibrillary actin, being surrounded by a positive signal for desmin. A differential diagnosis as to other conditions involving proliferation of CBs is discussed.

Transient cytoplasmic bodies in muscle of three infants with Werdnig-Hoffmann disease

We present three instances in which cytoplasmic bodies in muscle fibers were associated with Werdnig-Hoffmann disease. The children presented within the first 6 weeks of life with clinical symptoms and laboratory studies indicative of infantile spinomuscular atrophy (ISMA). Initial muscle biopsies in each case revealed signs of muscle immaturity and cytoplasmic bodies but lacked features of denervation. Follow-up biopsies in 2 cases revealed changes typical of ISMA, but cytoplasmic bodies were no longer present. A follow-up biopsy was not available in the third child who also had a clinical course consistent with ISMA. We discuss the pathogenesis of cytoplasmic bodies and their significance in association with Werdnig-Hoffmann disease.

The spectrum of cytoplasmic body myopathy: report of a congenital severe case

A 6-year-old girl presented with a myopathy--she was floppy since birth and developed progressive respiratory failure for which she required mechanical ventilation at age 6 months. Biopsy showed cytoplasmic bodies in about 15% of both type 1 and 2 muscle fibers. Of the 18 cases of cytoplasmic body myopathy (CBM) reported in the literature, 3 had symptoms at birth and in all of them the course was benign. Four clinical patterns emerged; a) congenital severe, b) congenital benign, c) juvenile severe and d) adult severe forms.

Ubiquitin is a common factor in intermediate filament inclusion bodies of diverse type in man, including those of Parkinson's disease, Pick's disease, and Alzheimer's disease, as well as Rosenthal fibres in cerebellar astrocytomas, cytoplasmic bodies in muscle, and mallory bodies in alcoholic liver disease

Polyclonal antibodies were raised which have a high affinity for conjugated ubiquitin. Immunocytochemistry was performed on paraffin sections of tissues showing well-characterized inclusion bodies. Ubiquitin was found as a component of the intermediate filament inclusion bodies characteristic of several major diseases including Lewy bodies of Parkinson's disease, Pick bodies of Pick's disease, Mallory bodies of alcoholic liver disease, cytoplasmic bodies of a specific myopathy, and Rosenthal fibres within astrocytes. Ubiquitin was also present in the three histological lesions characteristic of Alzheimer's disease. These observations suggest a fundamental role for ubiquitin in the formation of intermediate filament inclusion bodies in man, and have implications regarding the pathogenesis of these important diseases.

Induction of spheroid cytoplasmic bodies in a rat muscle by local tetanus

The term "cytoplasmic body" or "spheroid body" myopathy refers to a heterogeneous group of familial or sporadic diseases characterized primarily by the presence of abundant spheroid or cytoplasmic bodies in the muscles. The morphogenesis of these inclusions remains unclear. This article describes the induction and evolution of spheroid cytoplasmic bodies (SCBs) in the rat plantaris muscle (PL) with local tetanus, which was induced in rats by the injection of a minute amount of tetanus toxin. In contrast to the tetanized soleus muscle (SOL), which developed core fibers (central cores, minicore, target fiber, targetoid fiber, and rods), the tetanized PL produced numerous SCBs with a predictable time course. They were induced in both type 1 and 2 fibers of PL, which is composed predominantly (95%) of type 2 fibers, in contrast to SOL (85% type 1 fibers). Factors inducing SCBs may include immobilization, shortening, intact innervation, and disuse atrophy.

Cytoplasmic body myopathy. Report on a family and review of the literature

A 15-year-old girl who was seen for scoliosis presented with cardiorespiratory failure associated with a respiratory infection. She was found to have weakness predominant in the face, sternomastoid, proximal limb, respiratory, spinal and cardiac muscles. The serum creatine kinase level was slightly elevated and the electrocardiogram was abnormal. The electromyograph was consistent with a myopathy. The course was malignant. Her 14-year-old brother had similar findings and succumbed at the age of 14 and one-half years from cardiorespiratory failure. The mother had minimal weakness of proximal limb muscles since early life. The tendon reflexes were normal as was the serum creatine kinase level. The course was benign. On light microscopy the muscle biopsy in the girl showed fibre diameter variation, centrally placed nuclei, necrosis, fibrosis and cytoplasmic bodies. The muscle biopsy in the brother and mother had similar findings except that the inclusion bodies were not seen in the mother. On electron microscopy, the girl showed typical cytoplasmic bodies, involving predominantly type 1 fibres. The mother also had these structures. The literature is reviewed and the origin, pathogenesis and aetiology of the cytoplasmic body are discussed.