Neuromuscular transmission in the murine mutants "motor end-plate disease" and "jolting"

Mice with the inherited disorder "motor end-plate disease" suffered from a progressive neuromuscular weakness and muscular wasting. The weakness resulted from a failure of evoked transmitter release from the motor nerve terminals. The failure in transmission was all-or-nothing in nature. The numbers of muscle fibres in skeletal muscle and myelinated axons in several major nerve trunks were no different from normal. The loss in muscle bulk was caused by the neuromuscular defect and not from a loss of motor units or muscle fibres. The inherited murine disorder "jolting" was allelic with "motor end-plate disease". Affected "jolting" mice suffered no detectable morphological abnormality in skeletal muscle or peripheral nerve. The physiological properties of skeletal muscle and the characteristics of neuromuscular transmission were indistinguishable from normal.     

Pseudohypertrophic myopathy caused by cysticercosis. Report of a case

A 25 years old woman was admitted with a history of apparent hypertrophy of the calves, specially on the left, slight pain in the legs and difficulty in walking. Electromyography showed giant motor unit potentials with complete interference pattern. Biopsy of both gastrocnemii was performed revealing a cysticercus among inflammatory infiltrate and changes of the muscle fibers. Review of the literature disclosed 12 other reported cases. The age ranged from 10 to 35 years with a median of 25 years. Pseudohypertrophic myopathy due to cysticercosis has been found twice more common in males than in females. History of epilepsy and muscle pain occurs in about one half of the cases and muscle weakness in about one third of them. Usually there is simultaneous involvement of the upper and lower limb girdles. Myotonia is rare but subcutaneous nodules are frequently found. Our case is unique in the literature in which the pseudohypertrophy was confined to the legs and electromyography showed giant motor unit potentials. The pathogenesis of this condition is discussed and attention is called to the differential diagnosis with other pseudohypertrophic muscular conditions such as pseudohypertrophic muscular dystrophy, myotonia congenita, trichinosis, hypothyroidism, amyloidosis and glycogenosis of type I (Pompe's disease) in its juvenile form.     

Benign calf amyotrophy: clinicopathologic study of 8 patients

BACKGROUND: The benign focal amyotrophy disorders have been described since 1959 for the upper limbs and since 1981 for the lower limbs. The clinicopathologic features have pointed to a restricted and self-limiting form of motor neuron disease. OBJECTIVE: To describe the clinical, electromyographic, and muscle histopathologic features in 8 patients with benign calf amyotrophy. DESIGN: Retrospective review of patient charts, electromyograms, and muscle histopathology. PATIENTS AND RESULTS: Eight patients, aged 37 to 88 years, developed insidiously progressive calf muscle weakness and wasting during 1 to 5 years. The gastrocnemius weakness and wasting were bilateral in 4 patients. Initial progression of symptoms was followed by disease stabilization. None had a history of poliomyelitis or family history of neuromuscular disease. Creatine kinase values were mildly elevated in 5 patients. The electromyographic and muscle histopathologic findings were consistent with a chronic neuropathic disorder. Despite the restricted calf muscle involvement clinically, the electromyographic abnormalities suggested more diffuse lower limb involvement. Further studies, including DNA tests and muscle-based protein studies, excluded several types of inherited neuromuscular disorders. CONCLUSIONS: Benign calf amyotrophy is a variant of the benign focal amyotrophy disorders. The etiology for these disorders is unknown. Studies to exclude other causes of calf amyotrophy and careful follow-up examinations to document disease stabilization are necessary to diagnose this uncommon disorder.     

Muscle weakness in infants with rickets: distribution, course, and recovery

We describe the distribution, progression, and resolution of muscle weakness, wasting, and hypotonia in three infants with rickets due to different causes. Progressive muscle weakness affecting preferentially the proximal muscles of the legs and failure to gain weight were the presenting symptoms. The skeletal signs appeared later in the course of the illness and the time for resolution of the neuromuscular findings varied with the etiology of the disorder.     

Chromosome 12-linked autosomal dominant scapuloperoneal muscular dystrophy

Scapuloperoneal syndromes are characterized by their distribution of muscle weakness and wasting. The reported pattern of inheritance has been variable. Both neurogenic and myopathic forms of autosomally dominantly inherited scapuloperoneal syndrome have been described. It has been suggested that these are variants of other neuromuscular diseases. We examined 44 members from a family with 14 members affected with a scapuloperoneal syndrome. Physiological and histological analysis implied that this condition is predominantly myopathic. Linkage analysis was done to confirm the genetic etiology of the disease in this family and to evaluate the possibility that it is an allelic variant of other neuromuscular diseases. Genetic analysis demonstrated linkage of the disease to chromosome 12, which makes it genetically distinct from other loci known to cause neuromuscular disease. Muscle fibers with hyaline desmin-containing cytoplasmic inclusions in combination with focal myopathic changes may be a disease-specific morphological marker of the disease.     

A missense mutation in DYNC1H1 gene causing spinal muscular atrophy – Lower extremity,dominant

Spinal muscular atrophy (SMA) is a hereditary neuromuscular disorder, which causes progressive muscle weakness and in severe cases respiratory failure and death. Although the majority of the SMA cases are autosomal recessive, there is an autosomal dominant variant of SMA that primarily affects the lower extremities, known as ‘spinal muscular atrophy – lower extremity, dominant’ (SMALED). Mutations in the Dynein Cytoplasmic 1 Heavy Chain 1 (DYNC1H1) gene were the first to be associated with SMALED. Here we report a family with SMALED caused by a pathogenic heterozygous missense c.1809 A > T, p.glu603Asp mutation in DYNC1H1. The main clinical features were congenital hip displacement, talipes, delayed motor development, wasting and weakness in lower limbs with relative sparing of upper extremities and very slow disease progression.SMALED is extremely rare and only a handful of families have been reported. Over the years other phenotypes including Charcot Marie Tooth type 2 and hereditary mental retardation with cortical neural migration defects have also been reported to be caused by DYNC1H1 mutations.This report aims to increase our awareness of SMALED and various other phenotypes associated with mutations in this gene.     

Familial lethal cardiomyopathy with mental retardation and scapuloperoneal muscular dystrophy.

A family is described with a neuromuscular disorder characterised by possible X-linked recessive inheritance, a benign, slowly progressive muscular dystrophy with predominant humeroperoneal distribution and lack of contractures or pseudohypertrophy, central nervous system involvement, myopia and lethal cardiomyopathy. The possibility of cardiac transplant as life-saving therapy is suggested.     

Pena-Shokier phenotype: case presentation and review

Pena-Shokier phenotype is an early lethal disorder involving multiple joint contractures, facial anomalies, and pulmonary hypoplasia. Alternative terms for this syndrome used in the literature include fetal hypokinesia syndrome, lethal congenital contracture syndrome, and Pena-Shokier syndrome type I. The etiology for the early cases was attributed to neuromuscular disease, with deformations owing to weakness or paralysis of the motor unit. An abnormality of spinal cord motoneurons has been postulated in some cases. Pena-Shokier phenotype can also result from blockade of the neuromuscular junction, as shown by recent observations with women expressing antibodies against the fetal acetylcholine receptor. It has been shown that the Pena-Shokier phenotype may result from intrauterine cerebral dysfunction as well, including acquired brain insults and congenital brain malformations. The ultimate prognosis for children with this disorder is dependent on the underlying etiology and the severity of pulmonary disease. The authors report a fatal case of Pena-Shokier phenotype with congenital polymicrogyria. To our knowledge, the case presented is the first reported Pena-Shokier phenotype associated with this type of brain malformation.     

A family of Becker's progressive muscular dystrophy with severe cardiomyopathy

A family of Becker's muscular dystrophy with marked cardiomyopathy was studied. The propositus, a 16-year-old boy with marked pseudohypertrophy in calves, showed electrocardiographic abnormalities resembling those in the Duchenne's type. Radionuclide study and endomyocardial biopsy revealed remarkable degeneration of myocardium. His uncle, who also had slight proximal muscular atrophy and weakness, and calves' pseudohypertrophy, died of heart failure at the age of 47, and autopsy showed dystrophic changes in skeletal muscles and extensive myocardial damage. Severe cardiac involvement can occur in Becker's muscular dystrophy which has been known to have an essentially benign clinical course, and radionuclide investigation is useful for the detection of preclinical cardiac lesions in patients with muscular dystrophy.     

Severe neuropathy in a patient with acquired immune deficiency syndrome (AIDS)

Summary A patient with acquired immune deficiency syndrome (AIDS) developed a progressive neuromuscular disorder which included a sensory component, severe weakness and muscle wasting, and fasciculations. At autopsy, there was evidence of severe peripheral neuropathy, as well as widespread cytomegalovirus (CMV) infection within the central and peripheral nervous system. Although the anterior horn cell complement within the spinal cord appeared normal, there was also evidence of human immunodeficiency virus (HIV)-like immunoreactivity of rare anterior horn cells, as judged by immunohistochemical staining. This patient illustrates the complexity of pathogenetic mechanisms operative in AIDS patients with neuromuscular disease, and suggests that at least some examples of neuromuscular disease in patients with this syndrome may be related to widespread CMV infection of the peripheral nerve (including microvascular endothelial cells) and, more rarely, direct HIV infection of some anterior horn cells.H. V. V. is a recipient of a John Douglas French Foundation/Wilson Foundation fellowship     

Progressive skeletal muscle weakness in transgenic mice expressing CTG expansions is associated with the activation of the ubiquitin–proteasome pathway

Myotonic dystrophy type 1 (DM1) is a neuromuscular disease caused by the expansion of a CTG repeat in the DMPK gene and characterised by progressive skeletal muscle weakness and wasting. To investigate the effects of the CTG expansion on the physiological function of the skeletal muscles, we have used a transgenic mouse model carrying the human DM1 region with 550 expanded CTG repeats. Maximal force is reduced in the skeletal muscles of 10-month-old but not in 3-month-old DM1 mice when compared to age-matched non-transgenic littermates. The progressive weakness observed in the DM1 mice is directly related to the reduced muscle mass and muscle fibre size. A significant increase in trypsin-like proteasome activity and Fbxo32 expression is also measured in the DM1 muscles indicating that an atrophic process mediated by the ubiquitin–proteasome pathway may contribute to the progressive muscle wasting and weakness in the DM1 mice.     

Challenges and opportunities in clinical trials for spinal muscular atrophy

Spinal muscular atrophy (SMA) is the most common fatal neuromuscular disease of infancy. SMA type I is the most severe and mortality is usually due to respiratory failure. In type II the disability is of later onset and less severe, and prognosis has improved primarily due to supportive care. Type III is the mildest form with onset usually of weakness in adolescence or young adulthood. SMA is an autosomal recessive disorder with deletions or mutations of the gene at the 5 q11 locus. There is no specific prevention or treatment, but current progress toward potential therapies has been substantial and several candidates including histone deacetylase (HDAC) inhibitors are under consideration for further evaluation. The authors sought to address the challenges and opportunities for testing new therapies for SMA.     

Miller Fisher syndrome with presynaptic neuromuscular transmission disorder

Miller Fisher syndrome is defined by a triad of symptoms, namely areflexia, ataxia, and ophthalmoparesis. The ophthalmoparesis is mostly severe, undulating weakness of eye movements with ptosis and increased fatigability resembling a neuromuscular transmission disorder. We present a 52-year-old man with severe Miller Fisher syndrome with a high level of anti-GQ1b antibodies and a presynaptic type of neuromuscular transmission disorder. The diagnosis was confirmed by stimulated single-fiber electromyography with the use of a concentric needle electrode and various stimulation rates.     

Familial monomelic amyotrophy: a case report from India

Monomelic amyotrophy (MMA) is a benign lower motor neuron disorder in the young with male preponderance. It is characterized by insidious onset and progressive weakness and wasting of a distal extremity over a few years followed by spontaneous arrest. The exact pathogenesis is unknown. It is predominantly a sporadic disorder but rarely familial forms have been documented. In this report, we describe the phenotype of a 21-year-old man and his mother who were diagnosed to have MMA. The index case presented with left upper limb weakness and wasting of 3 years duration while his mother had right upper limb amyotrophy and weakness of 34 years. A total of 190 patients were diagnosed to have MMA in our institute over the last 27 years and this is the first case of familial MMA.     

Nemaline myopathy and a mitochondrial neuromuscular disorder in one family

A family composed of parents and four children is reported. Two brothers presented from early infancy with hypotonia and non-progressive weakness. Muscle biopsy in both revealed numerous typical nemaline rods. The father, suffering from backache, had a slow MNCV of both common peroneal nerves. His muscle revealed variation in fiber size, splitting, type 1 atrophy and numerous pleomorphic mitochondria with crystalline inclusions. The mother's muscle showed type 2 atrophy, foci of myofibrillar degeneration, and lipofuscin bodies. In a 12-year-old daughter and a 5-year-old son the muscle revealed an excess of small, bizarre mitochondria and lipid droplets. The coexistence of nemaline myopathy and a mitochondrial neuromuscular disorder in one family has never been reported in the literature. It might be a coincidence of two rare muscle disorders in one family, or it might be the polymorphic expression of a single etiological factor causing a defect in protein synthesis.     

Congenital myopathy with tubular aggregates and tubulofilamentous IBM-type inclusions

We report on a 16-year-old girl with a unique neuromuscular disorder characterised by progressive proximal muscle weakness and numerous tubular aggregates, intracytoplasmic, as well as intranuclear inclusions of the IBM type in her muscle biopsy. The clinical features of the presented case, as manifested by the early childhood onset of the disease, proximal weakness, lumbar hyperlordosis, and bilateral Achilles tendon contractures, were suggestive of congenital myopathy. To the best of our knowledge, the coexistence of tubular aggregates and tubulofilamentous inclusions of the IBM type in a child has never been described.     

Non hypertrophic amyloid myopathy with muscular inflammation in plasma cell dyscrasia]

The case of a 41 year old woman with amyloid myopathy is reported. Clinical involvement consisted of limb girdle muscle weakness, mild scapular muscle atrophy and dysphagia. In contrast with the published cases, abnormal firmness, pseudohypertrophy of the musculature and macroglossia were absent. Muscle biopsy showed endo- and perimysial amyloid deposits but also inflammatory infiltrates. Inflammatory cells typing was studied by immunocytochemical methods and revealed a predominant T-helper cell infiltration. Free kappa light chains were present in serum and urine. Serum immunoglobulin levels were reduced. Bone marrow examination revealed mild plasmocytosis without abnormal cells. Immunofluorescence and immunoperoxidase techniques for identification of the type of amyloid fibrils showed positivity with antisera to kappa light chains. A 4-year follow-up revealed a progressive worsening of muscle weakness despite immunosuppressive treatment. No malignant plasmocytosis occurred. The unusual inflammatory muscle infiltration observed in this case may suggest an associated polymyositis.     

Surprises of genetic engineering: a possible model of polyglucosan body disease.

BACKGROUND: The authors previously reported the generation of a knockout mouse model of Pompe disease caused by the inherited deficiency of lysosomal acid alpha-glucosidase (GAA). The disorder in the knockout mice (GAA-/-) resembles the human disease closely, except that the clinical symptoms develop late relative to the lifespan of the animals. In an attempt to accelerate the course of the disease in the knockouts, the authors increased the level of cytoplasmic glycogen by overexpressing glycogen synthase (GSase) or GlutI glucose transporter. METHODS: GAA-/- mice were crossed to transgenic mice overexpressing GSase or GlutI in skeletal muscle. RESULTS: Both transgenics on a GAA knockout background (GS/GAA-/- and GlutI/GAA-/-) developed a severe muscle wasting disorder with an early age at onset. This finding, however, is not the major focus of the study. Unexpectedly, the mice bearing the GSase transgene, but not those bearing the GlutI transgene, accumulated structurally abnormal polysaccharide (polyglucosan) similar to that observed in patients with Lafora disease, glycogenosis type IV, and glycogenosis type VII. Ultrastructurally, the periodic acid-Schiff (PAS)-positive polysaccharide inclusions were composed of short, amorphous, irregular branching filaments indistinguishable from classic polyglucosan bodies. The authors show here that increased level of GSase in the presence of normal glycogen branching enzyme (GBE) activity leads to polyglucosan accumulation. The authors have further shown that inactivation of lysosomal acid alpha-glucosidase in the knockout mice does not contribute to the process of polyglucosan formation. CONCLUSIONS: An imbalance between GSase and GBE activities is proposed as the mechanism involved in the production of polyglucosan bodies. The authors may have inadvertently created a "muscle polyglucosan disease" by simulating the mechanism for polyglucosan formation.     

Prolonged myasthenic syndrome after one week of muscle relaxants

A child developed severe, generalized muscle weakness which persisted for 6 weeks, after receiving muscle relaxants for 1 week while requiring ventilator support. Electrodiagnostic studies indicated a presynaptic disorder of the neuromuscular junction which improved with high-frequency stimulation, similar to findings in Lambert-Eaton syndrome. Muscle specimens exhibited neurogenic targetoid fiber atrophy. Ultrastructure of the neuromuscular junction indicated terminal axon degeneration and atrophy with depletion of the secretory vesicles. Most reported patients with post-ventilator paresis have received steroids and muscle relaxants; muscle weakness commonly has been brief and attributed to steroids. We believe that this reversible myasthenic syndrome probably represents neurotoxicity due to high doses of steroidal nondepolarizing blocking agents; however, available data are insufficient to resolve this controversy.