The spectrum of rod myopathies

Muscle cofilin alters neuromuscular junction postsynaptic development to strengthen functional neurotransmission

Cofilin, an actin severing protein, plays critical roles in muscle sarcomere addition and maintenance. Our previous work has shown Drosophila cofilin (DmCFL) knockdown causes progressive deterioration of muscle structure and function and produces features seen in nemaline myopathy (NM) caused by cofilin mutations. We hypothesized that disruption of actin cytoskeleton dynamics by DmCFL knockdown would impact other aspects of muscle development, and, thus, conducted an RNA sequencing analysis which unexpectedly revealed upregulated expression of numerous neuromuscular junction (NMJ) genes. We found that DmCFL is enriched in the muscle postsynaptic compartment and that DmCFL deficiency causes F-actin disorganization in this subcellular domain prior to the sarcomere defects observed later in development. Despite NMJ gene expression changes, we found no significant changes in gross presynaptic Bruchpilot active zones or total postsynaptic glutamate receptor levels. However, DmCFL knockdown results in mislocalization of glutamate receptors containing the GluRIIA subunit in more deteriorated muscles and neurotransmission strength is strongly impaired. These findings expand our understanding of cofilin's roles in muscle to include NMJ structural development and suggest that NMJ defects may contribute to NM pathophysiology.

Nebulin expression in patients with nemaline myopathy

Nemaline myopathy is a structural congenital myopathy which may show both autosomal dominant and autosomal recessive inheritance patterns. Mutations in three different genes have been identified as the cause of nemaline myopathy: the gene for slow alpha-tropomyosin 3 (TPM3) at 1q22-23, the nebulin gene (NEB) at 2q21.1-q22, and the actin gene (ACTA1) at 1q42. The typical autosomal recessive form appears to be the most common one and is caused by mutations in the nebulin gene. We have studied the pattern of nebulin labeling, in patients with the typical congenital form (ten patients), the severe congenital form (two patients) or the mild, childhood-onset form (one patient), using antibodies against three different domains of nebulin. A qualitative and quantitative nebulin analysis in muscle tissue showed the presence of nebulin in myofibers from all patients. Some differences relating to the rod structure were observed. The majority of the largest subsarcolemmal rods were not labeled with the N2 nebulin antibody (I-band epitope) and showed an indistinct pattern with the two antibodies directed to the Z-band portion of nebulin (epitopes M176-181 and serine-rich domain). Diffuse rods were not revealed using the three antibodies. A discordant pattern of nebulin N2 epitope labeling was found in two affected sisters with a mutation in the nebulin gene, suggesting that modifications in nebulin distribution inside the rods might occur with the progression of the disease. Western blot analysis showed no direct correlation with immunofluorescence data. In nine patients, the band had a molecular weight comparable to the normal control, while in one patient, it was detected with a higher molecular weight. Our results suggest that presence/absence of specific nebulin Z-band epitopes in rod structures is variable and could depend on the degree of rod organization.

Nemaline rods in canine myopathies: 4 case reports and literature review

The diagnosis of nemaline rod myopathy (NM) is based on the presence of numerous pathognomonic rods within a fresh frozen muscle biopsy specimen. Three forms of congenital NM have been described in humans, and rods have been found to occur in various other conditions. A similar myopathy was described in 1986 in a family of cats. In this report, we describe a case of congenital NM in a 10-month-old Border Collie, an adult-onset NM in an 11-year-old Schipperke, and 2 acquired myopathies with nemaline rods in adult dogs associated with hypothyroidism and Cushing's syndrome. Common clinical features included exercise intolerance, abnormal electromyography, and the presence of nemaline rods in fresh, frozen, and glutaraldehyde-fixed biopsies from proximal appendicular limb muscles. Staining of cryostat sections of muscle biopsy specimens by the modified Gomori trichrome technique disclosed numerous rod bodies that were localized to type 1 fibers by the histochemical adenosine triphosphatase reaction. Accumulation of rods also was demonstrated by electron microscopy in 2 of the cases with localized enlargement and streaming of Z lines. Documentation of NM in a young Border Collie and the adult-onset form in the Schipperke alerts clinicians to the existence of this disorder in these breeds.

Late-onset rod myopathy associated with monoclonal gammopathy

A 31-yr-old woman presented with a severe and rapidly progressive myopathy affecting proximal limbs, neck flexors and respiratory muscles. Muscle biopsy revealed numerous atrophic fibres with marked structural alterations, without inflammatory infiltrate. By electron microscopy, atrophic fibres displayed many rods. A benign monoclonal gammopathy (IgG, lambda chain) was evident in serum. A sarcolemmal deposit of IgG, lambda chain was found by immunostaining. Plasmapheresis and immunosuppressive therapies produced a decrease in paraproteinemia and a partial clinical improvement. This observation is the third to associate monoclonal gammopathy with "late-onset rod myopathy". The pathogenetic role of paraproteinemia remains unclear.

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.

Adult-onset rod disease with abundant intranuclear rods

The third case of adult-onset rod disease (nemaline myopathy) with abundant myofibrillar as well as intranuclear rods is described. The 61-year-old woman suffered from progressive weakness of proximal extremities and of the neck, mimicking polymyositis. Muscle biopsy revealed a striking myopathic pattern, with intranuclear rods occurring in 31% of the fibres. On light and electron microscopy and by immunohistochemical study, the rods differed from myofibrillar rods. The absence of alpha-actinin in intranuclear rods suggests an enhanced readiness of actin filaments to bind to diverse proteins, instead of overproduction of alpha-actinin as the pathogenetic basis of the rod formation.

Adult-onset mixed myopathy with nemaline rods, minicores, and central cores: a muscle disorder mimicking polymyositis

A woman, aged 75 years, presented with a 15-year history of progressive, generalized, painful muscle weakness and wasting. Clinical and laboratory investigation revealed a sporadic muscle disorder. Muscle biopsy showed a mixed pattern of nemaline myopathy with minicores and central cores and severe atrophy of type-1 and type-2 fibers. A trial of immunosuppressive treatment did not improve her condition, which clinically mimicked chronic progressive polymyositis. Mixed myofibrillar myopathies of this type have so far only been described among the group of congenital myopathies.

[Nemaline myopathy: report of a case with a histochemical and electron microscopy study]

Report of a case of a male child, with hypotonia since birth, along with severe feeding difficulties due to lack of swallowing, that resulted in a permanent gastrostomy. Despite the delayed motor development, he had a normal intelligence. An electromyography was suggestive of primary muscle involvement. A fresh-frozen muscle biopsy stained by the modified Gomori trichrome and processed by histochemistry and electron microscopy presented the typical nemaline rods and deficiency of type II muscle fibers. It is made a brief revision about the clinical symptoms, origin and pathogenesis of nemaline bodies. The case reported probably represents a nemaline myopathy, of the congenital type.

Nemaline rod disease, with reference to the routine use of histochemical methods in autopsy investigations

A 50-year-old man had suffered from an undiagnosed form of muscle disease for most of his life. Death was due to cardiac failure. Numerous samples of muscle, obtained at autopsy, were subjected to the usual histochemical techniques used in investigating neuromuscular disease. Frozen sections revealed the abnormal accumulations of Z-band protein that characterize nemaline rod disease. That this disorder would have escaped diagnosis had only routine paraffin-embedded sections been examined is emphasized.

A case of nemaline myopathy with ophthalmoplegia and mitochondrial abnormalities

A case of nemaline myopathy with ophthalmoplegia is reported. The patient was a 35-year-old man born of consanguineous parents. He had a myopathic face, high-arched palate, nasal voice, scoliosis, very thin trunk and marked muscle weakness involving face, neck, limbs and trunk. He also had ptotis of the left eyelid and mild bilateral ophthalmoplegia, also detected by electrooculogram. Biopsy of gastrocnemius muscle revealed nemaline rods. At the ultrastructural level, the rods appeared to have axial and cross striations, and in cross-sections at high magnification they seemed to have a crystal lattice structure. Intranuclear rods were also observed. In addition to the rods, abnormal mitochondria including a number of paracrystalline inclusions were seen.

Fine structural correlations between the muscle pathology of amyotrophic lateral sclerosis (ALS) patients and experimental Ca-Mg deficient rats

Nonspecific myofibrillar changes such as streaming of the Z-line, formation of rod-like structures, satellitosis, proliferation of sarcolemmal nuclei and papillary projection of the sarcolemma were recognized as a disorganization of the muscle itself. In addition, fine structural pathology in ALS specimens showed characteristically a pig-tail formation - 'Zopfformation' - which has been considered to have a neurogenic origin.

Congenital hypotonia revisited

The definition of neuromuscular diseases affecting infants has depended on factors as various as the rate of progression of the illness, the clinical picture, and, recently, the morphologic peculiarities in the muscle biopsy. A review of the literature suggests that there are discrepancies in the classification of such illnesses, no matter what system is used. In some instances, a single diagnosis seems to include patients with quite separate illnesses, whereas other patients with seemingly identical diseases have been given different diagnoses.

Fatal neonatal nemaline myopathy with multiple congenital anomalies

The clinical course and autopsy findings in a patient with fatal neonatal nemaline myopathy are described. A hypotonic infant required mechanical ventilatory support immediately following delivery and developed progressive congestive heart failure. He had mild facial dysmorphism, a high-arched palate, clinodactyly, short first metacarpals, abnormal dermatoglyphics, simian creases, and bilateral talipes varus. Light and electron microscopic study of a muscle biopsy was diagnostic of nemaline myopathy. Autopsy revealed a papillary muscle anomaly, myocardial scarring, and hepatic fibrosis. The severe clinical impairment in this infant and the unusual associated anomalies are compared with other examples of nemaline myopathy. Nemaline myopathy is a cause of respiratory insufficiency in the neonatal period.

Nemaline bodies in a progressive infantile neuromuscular disorder

Nemaline bodies are described in a case of a progressive neuromuscular disorder, which is difficult to classify. The clinical syndrome is not characteristic of a nemaline myopathy. It is argued that the finding of nemaline bodies is in itself not specific of any neuromuscular disease.

Nemaline myopathy: histological, histochemical and ultrastructural studies

Histological, histochemical and ultrastructural studies were performed on muscle biopsies from three siblings with congenital nemaline myopathy. Histological studies revealed type I fibre atrophy and type II fibre paucity. Ultrastructural studies of intramuscular nerves showed that the axonal diameters were very narrow compared with the width of myelin lamellae. Granular or membranous osmiophilic material occurred in the adaxonal Schwann cell cytoplasm and had a periodicity of 33--38 A. The neuromuscular junctions showed degenerative features such as glycogen granules or myelin figures in 27.1% of total terminal axons. The secondary synaptic clefts were markedly decreased in number and short in length. Myotendinous junction-like structures were found in 5.5% of the muscle fibres near the neuromuscular junctions, and often near sites of fibre-splitting. Rods in nemaline myopathy might be caused as a result of longitudinal splitting and disruption of fibres due to deficient regeneration of the muscle fibres associated with neurotrophic abnormalities.

Focal myositis

Focal myositis, a new distinct clinicopathologic entity, is a benign inflammatory pseudotumor of skeletal muscle. Based on a study of 16 cases, the disease which affects both children and adults typically evolves over a period of several weeks as a localized painful swelling within the soft tissue of an extremity. At surgery the lesion is frequently considered a neoplasm, appearing pale in color and poorly demarcated from the surrounding muscle. Histologically there is lymphocytic infiltration of the perimysial and endomysial spaces, scattered muscle fiber necrosis and regeneration, and interstitial fibrosis. The etiology is unknown, but a history of trauma or family background of a similar disease was specifically excluded. Although polymyositis may be suspected initially because of muscle pain and inflammation, the process remains confined to a single area and signs of systemic disease are not encountered. Follow-up information obtained 2--6 years after surgery indicates no recurrence of the lesion in any of 16 cases.

Benign vaginal rhabdomyoma: a light and electron microscopic study

A benign vaginal rhabdomyoma from a 49-year-old woman was examined by light and electron microscopy. While many of the ultrastructural features conformed to those noted in previously described rhabdomyomas, certain features are described for the first time. These include attachment plaques between cells enclosed within a common basement membrane, cytoplasmic bodies, and peripheral couplings. Finally, the literature is reviewed and the reported cases of rhabdomyoma are divided into adult and fetal types based upon light microscopic criteria.