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

Floppy infant syndrome

Floppiness/hypotonia is a common neurologic symptom in infancy. A variety of neuromuscular disorders and central nervous system (CNS) disorders cause floppy infant syndrome (FIS). CNS disorders are the much more common causes of the syndrome than neuromuscular disorders. On long-term follow up, cerebral palsy and mental retardation turn out to be the 2 most common causes of FIS. This review focuses on neuromuscular causes of FIS. With the advent of molecular diagnosis, a few conditions can be diagnosed by DNA analysis of the peripheral lymphocytes (myotonic dystrophy, spinal muscular atrophy); however, for the most part, electrodiagnostic studies and muscle biopsy remain as essential diagnostic tools for FIS. Immunohistochemical study of the biopsied muscle also improves diagnostic capability. Management for most conditions remains supportive.

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."

Severe infantile congenital myopathy with nemaline and cytoplasmic bodies: a case report

A Japanese boy had marked generalized hypotonia and weakness and progressive respiratory failure since birth. Left biceps brachii muscle biopsy at 47 days of age showed marked variation in muscle fiber size, and nemaline and/or cytoplasmic bodies in approximately 10% of the muscle fibers. To our knowledge, the presence of nemaline and cytoplasmic bodies in the same muscle has not been previously reported. The severity of his respiratory failure and muscle weakness were thought to be related to muscle immaturity since there were many undifferentiated type 2C fibers.

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 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.

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.

Congenital myopathies

About forty different congenital myopathies (CM) are defined by clinical and morphological criteria. Classical types like central core disease, centronuclear myopathy, and nemaline/rod myopathy are now well established and recognized as neuromuscular conditions. Clinical subtypes as infantile, juvenile, and adult forms have been recognized in several CM. Not infrequently, different disease-specific morphological features may occur in muscle tissue of the same patient combined. Other CM are marked by aggregates of desmin filaments indicating the importance of recent immunohistochemical techniques. Modern myopathological techniques enabled nosological separation of CM, immunohistochemistry, actually, may usher in a new period of research in and understanding of CM. However, application of molecular genetic and molecular biological methods to CM may clarify still unsolved aspects of gene localisation for which the hereditary nature of many CM is particularly conducive, aspects of heterogeneity versus homogeneity of certain CM or clinical variants, of prenatal diagnosis of CM, of pathogenetic and nosological significance of muscle fiber proteins in CM, and of a new nosological classification of CM.

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.