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Magnesium (Mg) competes with calcium in normal synaptic transmission, inhibiting neurotransmitter release. As a drug, it is usually given as a treatment for eclampsia and pre-eclampsia. Two eclamptic pregnant women treated with Mg developed a pseudo-coma state immediately after emergency Caesarian Section. The clinical presentation was flaccid quadriparesis, areflexia, an absence of absent respiratory effort and vestibular-ocular reflexes, but with preserved pupillary responses. Decremental responses on repetitive nerve stimulation were found in both women. Recovery was obtained after cessation of the Mg. The persistence of pupillary reflexes in the absence of reflexes involving striated muscles was an important clinical clue, indicating neuromuscular junction dysfunction.

Dysphagia (impaired swallowing) is not a rare problem in various neuromuscular disorders, both in the pediatric and the adult patient population. On many occasions such patients are first presented to other medical specialists or health professionals. Disorders of deglutition are probably underrecognized in patients with a neuromuscular disease as a result of patient's and doctor's delay. This review will focus on dysphagia in adults suffering from a myopathy. Dysphagia in myopathies usually affects the oropharyngeal phases which rely mostly on voluntary muscle activity of the mouth, pharynx and upper esophageal sphincter. Dysphagia is known to contribute to a reduction of quality of life and may also lead to increased morbidity and mortality. The review includes an overview on symptomatology and tools of assessments, and elaborates on dysphagia in specific hereditary and acquired myopathies.

Background: GNE myopathy is a unique adult onset rare neuromuscular disease caused by recessive mutations in the GNE gene. The pathophysiological mechanism of this disorder is not well understood and to date, there is no available therapy for this debilitating disease. We have previously established proof of concept that AAV based gene therapy can effectively deliver the wild type human GNE into cultured muscle cells from human patients and in mice, using a CMV promoter driven human wild type GNE plasmid delivered through an adeno associated virus (AAV8) based platform. Objective: In the present study we have generated a muscle specific GNE construct, driven by the MCK promoter and packaged with the AAVrh74 serotype for efficacy evaluation in an animal model of GNE Myopathy. Methods: The viral vector was systemically delivered at 2 doses to two age groups of a Gne–/– hGNED207V Tg mouse described as a preclinical model of GNE Myopathy, and treatment was monitored for long term efficacy. Results: In spite of the fact that the full described characteristics of the preclinical model could not be reproduced, the systemic injection of the rAAVrh74.MCK.GNE viral vector resulted in a long term presence and expression of human wt GNE in the murine muscles and in some improvements of their mild phenotype. The Gne–/– hGNED207V Tg mice are smaller from birth, but cannot be differentiated from littermates by muscle function (grip strength and Rotarod) and their muscle histology is normal, even at advanced age. Conclusions: The rAAVrh74.MCK.GNE vector is a robust tool for the development of GNE Myopathy therapies that supply the intact GNE. However, there is still no reliable animal model to fully assess its efficacy since the previously developed Gne–/– hGNED207V Tg mice do not present disease characteristics.

POLR3A encodes the largest subunit of the DNA-dependent RNA polymerase III. Pathogenic variants in this gene are associated with dysregulation of tRNA production and other non-coding RNAs. POLR3A-related disorders include variable phenotypes. The genotype-phenotype correlation is still unclear. Phenotypic analysis and exome sequencing were performed in four affected siblings diagnosed clinically with hereditary spastic ataxia, two healthy siblings and their unaffected mother. All four affected siblings (ages 46-55) had similar clinical features of early childhood-onset hypodontia and adolescent-onset progressive spastic ataxia. None had progeria, gonadal dysfunction or dysmorphism. All affected individuals had biallelic POLR3A pathogenic variants composed by two cis-acting intronic splicing-altering variants, c.1909 + 22G > A and c.3337-11 T > C. The two healthy siblings had wild-type alleles. The mother and another unaffected sibling were heterozygous for the allele containing both variants. This is the first report addressing the clinical consequence associated with homozygosity for a unique pathogenic intronic allele in the POLR3A gene. This allele was previously reported in compound heterozygous combinations in patients with Wiedemann-Rautenstrauch syndrome, a severe progeroid POLR3A-associated phenotype. We show that homozygosity for this allele is associated with spastic ataxia with hypodontia, and not with progeroid features. These findings contribute to the characterization of genotype-phenotype correlation in POLR3A-related disorders.

Background The COVID-19 pandemic presents two main concerns for patients with myasthenia gravis (MG); chronic immunosuppression may put them at greater risk, and some proposed treatments for COVID-19 could cause MG exacerbation. Case description We present three patients with generalized seropositive MG who developed COVID-19. All patients had a favorable outcome, with only one patient experiencing exacerbation. In this case, exacerbation began before COVID-19; she required ICU admission, non-invasive ventilatory support, and received hydroxychloroquine, lopinavir and ritonavir which were well tolerated. One patient received IVIG in place of scheduled plasma exchange. Conclusion Outcome was favorable in all cases despite immunosuppressive therapy, use of experimental COVID-19 medication and switching of plasma exchange for IVIG., Highlights • Three cases of myasthenia gravis with COVID-19 with favorable outcome. • Immunosuppressive therapy was continued during COVID-19 infection. • Switching maintenance plasmapheresis with IVIg was well tolerated.

Dysphagia is one of the primary symptoms experienced by individuals with Oculopharyngeal Muscular Dystrophy (OPMD). However, we lack understanding of the discrete changes in swallowing physiology that are seen in OPMD, and the resulting relationship to impairments of swallowing safety and efficiency. This study sought to describe the pathophysiology of dysphagia in a small sample of patients with OPMD using a videofluoroscopy examination (VFSS) involving 3 × 5 mL boluses of thin liquid barium (22% w/v). The aim of this study is to extend what is known about the pathophysiology of dysphagia in OPMD, by quantifying changes in swallow timing, kinematics, safety, and efficiency, measured from VFSS. This study is a secondary analysis of baseline VFSS collected from 11 adults (4 male), aged 48-62 (mean 57) enrolled in an industry-sponsored phase 2 therapeutic drug trial. Blinded raters scored the VFSS recordings for safety [Penetration-Aspiration Scale (PAS)], efficiency [Normalized Residue Ratio Scale (NRRS)], timing [Pharyngeal Transit Time (PTT), Swallow Reaction Time (SRT), Laryngeal Vestibule Closure Reaction Time (LVCrt), Upper Esophageal Sphincter Opening Duration (UESD)], and kinematics (hyoid movement, pharyngeal constriction, UES opening width). Impairment thresholds from existing literature were defined to characterize swallowing physiology and function. Further, Fisher's Exact tests and Pearson's correlations were used to conduct a preliminary exploration of associations between swallowing physiology (e.g., kinematics, timing) and function (i.e., safety, efficiency). Compared to published norms, we identified significant differences in the degree of maximum pharyngeal constriction, hyoid movement distance and speed, as well as degree and timeliness of airway closure. Unsafe swallowing (PAS ≥ 3) was seen in only 3/11 patients. By contrast, clinically significant residue (i.e., NRRS scores ≥ 0.09 vallecular; ≥ 0.2 pyriform) was seen in 7/11 patients. Fisher's Exact tests revealed associations between prolonged SRT, PTT, and unsafe swallowing. Weak associations were also identified between post-swallow residue and poor pharyngeal constriction during the swallow. Detailed analysis of swallowing physiology in this series of adults with OPMD aligns with impaired muscular function (e.g., reduced pharyngeal constriction, incomplete laryngeal vestibule closure) associated with the disease, and primary functional challenges with swallow efficiency. Further work is needed to explore a greater range of food and liquid textures, and to identify additional physiological mechanisms underlying swallowing impairment in OPMD.

Background Mutations in GNE cause a recessive, adult onset myopathy characterized by slowly progressive distal and proximal muscle weakness. Knock-in mice carrying the most frequent mutation in GNE myopathy patients, GneM743T/M743T, usually die few days after birth from severe renal failure, with no muscle phenotype. However, a spontaneous sub-colony remains healthy throughout a normal lifespan without any kidney or muscle pathology. Objective We attempted to decipher the molecular mechanisms behind these phenotypic differences and to determine the mechanisms preventing the kidney and muscles from disease. Methods We analyzed the transcriptome and proteome of kidneys and muscles of sick and healthy GneM743T/M743T mice. Results The sick GneM743T/M743T kidney was characterized by up-regulation of extra-cellular matrix degradation related processes and by down-regulation of oxidative phosphorylation and respiratory electron chain pathway, that was also observed in the asymptomatic muscles. Surprisingly, the healthy kidneys of the GneM743T/M743T mice were characterized by up-regulation of hallmark muscle genes. In addition the asymptomatic muscles of the sick GneM743T/M743T mice showed upregulation of transcription and translation processes. Conclusions Overexpression of muscle physiology genes in healthy GneM743T/M743T mice seems to define the protecting mechanism in these mice. Furthermore, the strong involvement of muscle related genes in kidney may bridge the apparent phenotypic gap between GNE myopathy and the knock-in GneM743T/M743T mouse model and provide new directions in the study of GNE function in health and disease.

Adult polyglucosan body disease (APBD) is a rare glycogenosis manifesting progressive spastic paraparesis, sensorimotor polyneuropathy and neurogenic bladder. Misdiagnosis of APBD may lead to unnecessary investigations and to potentially harmful therapeutic interventions. To examine the frequency of misdiagnosis of APBD, we retrospectively reviewed the clinical data of 30 patients diagnosed between 1991 and 2013. Diagnosis was based on the combination of typical clinical and imaging findings, reduced glycogen branching enzyme activity, and the presence of p.Y326S GBE1 mutation. Initial symptoms started in the 5th-6th decade with bladder dysfunction (47 %), gait problems (33 %) or both. Diagnosis of APBD was delayed by 6.8 (±4.8) years. Consistent signs at diagnosis were spasticity in the legs (93 %), decreased or absent ankle reflexes (100 %), bilateral extensor plantar response (100 %) and distal sensory deficit (80 %). Nerve conduction study showed invariable sensorimotor polyneuropathy, and MRI demonstrated cervical spinal cord atrophy (100 %) and leukoencephalopathy (97 %). All 30 patients were initially misdiagnosed. Common misdiagnoses included cerebral small vessel disease (27 %), multiple sclerosis (17 %), amyotrophic lateral sclerosis (17 %) and peripheral neuropathies (20 %). Consequently, 27 % received inappropriate therapy. In addition, lower urinary tract symptoms in 60 % of men were attributed solely to prostatic disorders but did not respond to medical treatment or prostatectomy. These findings suggest that despite limited clinical variability, APBD is invariably misdiagnosed and patients are often mistreated. Physicians' unfamiliarity with the typical clinical and imaging features of APBD appears as the main reason for misdiagnosis.

GNE myopathy is an autosomal recessive muscle disease caused by biallelic mutations in GNE, a gene encoding for a single protein with key enzymatic activities, UDP-N-acetylglucosamine 2-epimerase and N-acetylmannosamine kinase, in sialic acid biosynthetic pathway. The diagnosis should be considered primarily in patients presenting with distal weakness (foot drop) in early adulthood (other onset symptoms are possible too). The disease slowly progresses to involve other lower and upper extremities' muscles, with marked sparing of the quadriceps. Characteristic findings on biopsies of affected muscles include 'rimmed' (autophagic) vacuoles, aggregation of various proteins and fibre size variation. The diagnosis is confirmed by sequencing of the GNE gene. Note that we use a new mutation nomenclature based on the longest transcript (GenBank: NM_001128227), which encodes a 31-amino acid longer protein than the originally described one (GenBank: NM_005476), which has been used previously in most papers. Based upon the pathophysiology of the disease, recent clinical trials as well as early gene therapy trials have evaluated the use of sialic acid or N-acetylmannosamine (a precursor of sialic acid) in patients with GNE myopathy. Now that therapies are under investigation, it is critical that a timely and accurate diagnosis is made in patients with GNE myopathy.

Myosin myopathies comprise a group of inherited diseases caused by mutations in myosin heavy chain (MyHC) genes. Homozygous or compound heterozygous truncating MYH2 mutations have been demonstrated to cause recessive myopathy with ophthalmoplegia, mild-to-moderate muscle weakness and complete lack of type 2A muscle fibers. In this study, we describe for the first time the clinical and morphological characteristics of recessive myosin IIa myopathy associated with MYH2 missense mutations. Seven patients of five different families with a myopathy characterized by ophthalmoplegia and mild-to-moderate muscle weakness were investigated. Muscle biopsy was performed to study morphological changes and MyHC isoform expression. Five of the patients were homozygous for MYH2 missense mutations, one patient was compound heterozygous for a missense and a nonsense mutation and one patient was homozygous for a frame-shift MYH2 mutation. Muscle biopsy demonstrated small or absent type 2A muscle fibers and reduced or absent expression of the corresponding MyHC IIa transcript and protein. We conclude that mild muscle weakness and ophthalmoplegia in combination with muscle biopsy demonstrating small or absent type 2A muscle fibers are the hallmark of recessive myopathy associated with MYH2 mutations.

GNE myopathy (previous names: HIBM, DMRV, IBM2) is a unique distal myopathy with quadriceps sparing. This recessively inherited myopathy has been diagnosed in various regions of the world with more than 150 disease-causing mutations already identified. Several of those are proven or suspected to be founder mutations in certain regional clusters and are described in this review. The review also discusses some historical aspects that might be relevant to the mutational distribution.

Background GNE Myopathy (GNEM) is a progressive adult-onset myopathy likely caused by deficiency of sialic acid (SA) biosynthesis. Objective Evaluate the safety and efficacy of SA (delivered by aceneuramic acid extended-release [Ace-ER]) as treatment for GNEM. Methods A Phase 2, randomized, double-blind, placebo-controlled study evaluating Ace-ER 3 g/day or 6 g/day versus placebo was conducted in GNEM subjects (n = 47). After the first 24 weeks, placebo subjects crossed over to 3 g/day or 6 g/day for 24 additional weeks (dose pre-assigned during initial randomization). Assessments included serum SA, muscle strength by dynamometry, functional assessments, clinician- and patient-reported outcomes, and safety. Results Dose-dependent increases in serum SA levels were observed. Supplementation with Ace-ER resulted in maintenance of muscle strength in an upper extremity composite (UEC) score at 6 g/day compared with placebo at Week 24 (LS mean difference +2.33 kg, p = 0.040), and larger in a pre-specified subgroup able to walk ≥200 m at Screening (+3.10 kg, p = 0.040). After cross-over, a combined 6 g/day group showed significantly better UEC strength than a combined 3 g/day group (+3.46 kg, p = 0.0031). A similar dose-dependent response was demonstrated within the lower extremity composite score, but was not significant (+1.06 kg, p = 0.61). The GNEM-Functional Activity Scale demonstrated a trend improvement in UE function and mobility in a combined 6 g/day group compared with a combined 3 g/day group. Patients receiving Ace-ER tablets had predominantly mild-to-moderate AEs and no serious adverse events. Conclusions This is the first clinical study to provide evidence that supplementation with SA delivered by Ace-ER may stabilize muscle strength in individuals with GNEM and initiating treatment earlier in the disease course may lead to better outcomes.

The objective of the study was to evaluate the epidemiology of patients with congenital myasthenic syndrome (CMS) in Israel. Targeted mutation analysis was performed based on the clinical symptoms and electrophysiological findings for known CMS. Additional specific tests were performed in patients of Iranian and/or Iraqi Jewish origin. All medical records were reviewed and clinical data, genetic mutations and outcomes were recorded. Forty-five patients with genetic mutations in known CMS genes from 35 families were identified. Mutations in RAPSN were identified in 13 kinships in Israel. The most common mutation was c.-38A>G detected in 8 patients of Iranian and/or Iraqi Jewish origin. Four different recessive mutations in COLQ were identified in 11 kinships, 10 of which were of Muslim-Arab descent. Mutations in CHRNE were identified in 7 kinships. Less commonly detected mutations were in CHRND, CHAT, GFPT1 and DOK7. In conclusion, mutations in RAPSN and COLQ are the most common causes of CMS in our cohort. Specific mutations in COLQ, RAPSN, and CHRNE occur in specific ethnic populations and should be taken into account when the diagnosis of a CMS is suspected.

We present further developments in the study of the antisense oligonucleotide EN101. Ongoing in vitro and in vivo studies demonstrate that EN101 is a TLR9-specific ligand that can suppress pro-inflammatory functions and shift nuclear factor kappa B (NF-κB) from the pro-inflammatory canonical pathway to the anti-inflammatory alternative pathway, which results in decreases acetylcholinesterase (AChE) activity. Preliminary results of a double-blinded phase II cross-over study compared 10, 20, and 40 mg EN101 administered to patients with myasthenia gravis. Patients were randomly assigned to one of three treatment groups in weeks 1, 3, and 5 and received their pretreatment dose of pyridostigmine in weeks 2 and 4. Thus far, all doses show a decrease in QMG scores, with a greater response to higher doses.

GNE myopathy is an autosomal recessive adult onset disorder caused by mutations in the GNE gene. GNE encodes the bifunctional enzyme UDP-N-acetylglucosamine 2-epimerase/N-acetyl mannosamine kinase, the key enzyme in the biosynthesis pathway of sialic acid. Additional functions for GNE have been described recently, but the mechanism leading from GNE mutation to this myopathy is unclear. Therefore a gene therapy approach could address all potential defects caused by GNE mutations in muscle. We show that AAV8 viral vectors carrying wild type human GNE cDNA are able to transduce murine muscle cells and human GNE myopathy-derived muscle cells in culture and to express the transgene in these cells. Furthermore, the intravenous administration of this viral vector to healthy mice allows expression of the GNE transgene mRNA and of the coexpressed luciferase protein, for at least 6months in skeletal muscles, with no clinical or pathological signs of focal or general toxicity, neither from the virus particles nor from the wild type human GNE overexpression. Our results support the future use of an AAV8 based vector platform for a safe and efficient therapy of muscle in GNE myopathy.

The recessively inherited, adult onset, quadriceps sparing myopathy with a predilection for distal muscles has received multiple historic names. The disorder was described in 1981 in Japanese patients and termed Nonaka Distal Myopathy [1], later commonly referred to as Distal Myopathy with Rimmed Vacuoles (DMRV) (OMIM#605820). In 1984, the disorder was described as vacuolar myopathy sparing the quadriceps in Iranian-Jewish patients [2], later commonly referred to as Inclusion Body Myopathy 2 (IBM2) or Hereditary Inclusion Body Myopathy (HIBM) (OMIM#600737). Mapping of the causative gene to the same locus on chromosome 9 in different cohorts of patient [3, 4], and ultimately identification of mutations in the causative gene GNE in all cohorts [5, 6], confirmed that these myopathies are in fact the same condition. However, since identification of GNE as the common causative gene, the multiple historic names for the disorder continue to be used by research groups worldwide. This disease nomenclature becomes increasingly confusing for clinicians, patients and researchers. Therefore, an international consortium (of which the authors are also members) has recently proposed to rename the disorder “GNE myopathy”, substituting all previous disease definitions. We all are now using this new name and hope that it will become the only term worldwide. After initial discovery of GNE gene defects to be causative for GNE myopathy, eight different GNE mRNA splice variants were identified, encoding (at least theoretically) eight protein isoforms [7]. The human GNE gene (GenBank Gene ID: 10020, {"type":"entrez-nucleotide","attrs":{"text":"NC_000009","term_id":"568815589","term_text":"NC_000009"}}NC_000009; ENSEMBL ENSG00000159921) consists of 13 exons, but each of the individual GNE mRNA splice variants consists of fewer exons. However, for mutation annotation purposes, only two major transcripts are relevant, which together span all 13 exons (Figure 1) [7]. We provide NCBI GenBank accession numbers for the two major isoforms hGNE1 and hGNE2 in the text below, and provide their ENSEMBL IDs in Table 1. Figure 1 Human GNE mRNA transcripts and isoforms. Table 1 Most frequent GNE myopathy-associated GNE variants hGNE1 (GenBank {"type":"entrez-protein","attrs":{"text":"NP_005467","term_id":"4885285","term_text":"NP_005467"}}NP_005467) is the originally described GNE protein which covers 722 amino acids [5] and is, confusingly, encoded in GenBank by mRNA transcript variant 2 ({"type":"entrez-nucleotide","attrs":{"text":"NM_005476","term_id":"298566309","term_text":"NM_005476"}}NM_005476). The hGNE2 isoform ({"type":"entrez-protein","attrs":{"text":"NP_001121699","term_id":"190014632","term_text":"NP_001121699"}}NP_001121699) covers 753 amino acids and is encoded by the longest GNE mRNA transcript, variant 1 ({"type":"entrez-nucleotide","attrs":{"text":"NM_001128227","term_id":"298566310","term_text":"NM_001128227"}}NM_001128227). The discovery of the additional N-terminal sequence (and novel exon 1) [8] encoding hGNE2, is potentially confusing since most previous molecular and biochemical studies (including all mutation reports) refer to the hGNE1 isoform, while according to universally adapted gene/protein nomenclature rules the longest mRNA splice form ought to be used for annotating nucleotide/amino acid locations (http://www.hgvs.org/mutnomen/refseq.html). Hence, amino acid numbering of previously reported GNE studies (based on hGNE1 nomenclature), including patient mutation reports, should be supplemented with 31 amino acids to adhere to the current (hGNE2) nomenclature guidelines, and nucleotide numbering should be supplemented with 93 bases. For exon numbering, the numbering according to the entire 13 exon GNE gDNA gene ought to be used, which means that exon numbering of previously reported GNE studies (based on hGNE1 nomenclature) have to be supplemented with one exon. Adaptation to the hGNE2 nomenclature can initially be confusing; however, we strongly support adaptation of this ‘new’ nomenclature. Laboratories/researchers not familiar with the GNE myopathy field and disease/gene history will report patient mutations and research tools (antibodies, enzyme activities, siRNA, nextgen sequence databases, etc.) according to current universally adapted nomenclature rules. Moreover, although there are no variants reported yet in the additional 31 amino acids of hGNE2 (perhaps because this region has not been considered for mutation analysis in many patients), future variants in this region could not be accurately named using hGNE1 as a reference. To illustrate the new terminology, we list both hGNE2 (‘new’ nomenclature) and hGNE1 (previous nomenclature) classifications and up to date exon numbers of the most frequent GNE mutations associated with GNE myopathy in Table 1. However, since history will leave its tracks, we strongly suggest accompanying all future references to GNE with the appropriate GenBank accession numbers.

To review some management issues in myasthenic disorders that are not part of the immune interventions. These are mainly related to pharmacotherapy of these conditions and side effects of various medications, but also referred to acute management of respiration in myasthenic crises.Antisense compound inhibiting acetylcholine esterase has positive therapeutic effects during short-term administration, but further studies are needed to confirm its chronic effects. Pyridostigmine seems not to have an additional effect to 3-4 diaminopyridine in Lambert Eaton myasthenic syndrome. Bilevel positive airway pressure and other external respiratory supportive systems may prevent in some myasthenic crises the need for intubation or at least shorten it. Statins can aggravate myasthenia gravis but the risk is not well quantified, and these compounds are not completely contraindicated in myasthenia.Further research of the above findings is still necessary to make them a solid conclusion for the management of the myasthenias.

Acetylcholinesterase pre-mRNA is susceptible to alternative splicing. Myasthenia gravis has been shown to be associated with the expression of the readthrough transcript (AChE-R), which, unlike the normal "synaptic" transcript (AChE-S) is not tethered to the post-synaptic membrane, but is a soluble monomer in the synaptic cleft. In rats with experimental autoimmune myasthenia gravis (EAMG), inhibition of production of AChE-R using antisense is associated with a significant reduction in synaptic expression of AChE-R mRNA and protein, with improved muscle strength and stamina and increased survival. Synaptic AChE does not appear to be significantly affected by the induction of EAMG or treatment with antisense to AChE-R. Monarsen (EN101) is a synthetic 20-base antisense oligodeoxynucleotide directed against the human AChE gene. It is modified to achieve stability for oral administration. Sixteen patients with seropositive myasthenia gravis who were responsive to pyridostigmine were withdrawn from it and treated with Monarsen. Fourteen patients experienced a clinically significant response. In some, the improvement was dramatic. Although the dose of pyridostigmine was not optimized before the study, the majority of responders achieved better Quantitative Myasthenia Gravis scores than on pyridostigmine. The response of an individual muscle group to Monarsen was related to the degree of deterioration following the withdrawal of pyridostigmine. Cholinergic side effects were conspicuous by their absence. Monarsen is now being investigated in a phase II study.

Charcot-Marie-Tooth type 1A (CMT1A) is an autosomal dominant polyneuropathy due to a 1.5 Mb tandem duplication in chromosome 17p11.2, containing the PMP22 gene. This mutation is not modified during inheritance. We set forth to test the hypothesis that in a subgroup of CMT1A patients there is clinical anticipation, namely an increase in disease severity over generations. Thirty-nine CMT1A mutation-positive patients in 16 families and 23 parent-offspring pairs were evaluated. This included 14 families with 2 generations and 2 families with 3 generations. Age of presentation was assessed by interviewing the patients and clinical severity was measured using the CMT neuropathy score (CMTNS). In 21/23 parent-child pairs and 14/16 families, there was an earlier age of presentation in children of genetically affected parents. The mean age of onset in the progeny was 12.61 years compared to 41.22 years in the parent generation, (p < 0.001).Mean severity in the younger generation was slightly higher than that of the parent generation. When corrected for the age difference, the trend for a worse phenotype in the younger generation became statistically significant (p < 0.02,Wilcoxon signed rank test). Our findings suggest that in a subgroup of CMT1A patients there is an increase in clinical severity over generations. The mechanism responsible for this observation remains unknown. Our findings should be validated on a larger cohort of CMT1A families.

Importance Preclinical studies have shown that neurotrophic growth factors (NTFs) extend the survival of motor neurons in amyotrophic lateral sclerosis (ALS) and that the combined delivery of these neurotrophic factors has a strong synergistic effect. We have developed a culture-based method for inducing mesenchymal stem cells (MSCs) to secrete neurotrophic factors. These MSC-NTF cells have been shown to be protective in several animal models of neurodegenerative diseases. Objective To determine the safety and possible clinical efficacy of autologous MSC-NTF cells transplantation in patients with ALS. Design, Setting, and Participants In these open-label proof-of-concept studies, patients with ALS were enrolled between June 2011 and October 2014 at the Hadassah Medical Center in Jerusalem, Israel. All patients were followed up for 3 months before transplantation and 6 months after transplantation. In the phase 1/2 part of the trial, 6 patients with early-stage ALS were injected intramuscularly (IM) and 6 patients with more advanced disease were transplanted intrathecally (IT). In the second stage, a phase 2a dose-escalating study, 14 patients with early-stage ALS received a combined IM and IT transplantation of autologous MSC-NTF cells. Interventions Patients were administered a single dose of MSC-NTF cells. Main Outcomes and Measures The primary end points of the studies were safety and tolerability of this cell therapy. Secondary end points included the effects of the treatment on various clinical parameters, such as the ALS Functional Rating Scale–Revised score and the respiratory function. Results Among the 12 patients in the phase 1/2 trial and the 14 patients in the phase 2a trial aged 20 and 75 years, the treatment was found to be safe and well tolerated over the study follow-up period. Most of the adverse effects were mild and transient, not including any treatment-related serious adverse event. The rate of progression of the forced vital capacity and of the ALS Functional Rating Scale–Revised score in the IT (or IT+IM)–treated patients was reduced (from −5.1% to −1.2%/month percentage predicted forced vital capacity, P P = .052) during the 6 months following MSC-NTF cell transplantation vs the pretreatment period. Of these patients, 13 (87%) were defined as responders to either ALS Functional Rating Scale–Revised or forced vital capacity, having at least 25% improvement at 6 months after treatment in the slope of progression. Conclusions and Relevance The results suggest that IT and IM administration of MSC-NTF cells in patients with ALS is safe and provide indications of possible clinical benefits, to be confirmed in upcoming clinical trials. Trial Registration clinicaltrials.gov Identifiers:NCT01051882andNCT01777646

Genetic analysis of clinical phenotypes in consanguineous families is complicated by co-inheritance of large DNA regions carrying independent variants. Here we characterized a family with early onset cone-rod dystrophy (CRD) and muscular dystrophy. Homozygosity mapping followed by whole exome sequencing revealed a nonsense mutation, p.R270*, in ALMS1 and two novel potentially disease-causing missense variants, p.R1581C and p.Y2070C, in DYSF. ALMS1 and DYSF are genetically and physically linked on chromosome 2 in a genomic region suggested by homozygosity mapping and associated with Alström syndrome, which includes CRD, and with limb girdle muscular dystrophy, respectively. Affected family members lack additional systemic manifestations of Alström syndrome but exhibit mild muscular dystrophy. RNA-seq data did not reveal any significant variations in ALMS1 transcripts in the human retina. Our study thus implicates ALMS1 as a non-syndromic retinal disease gene and suggests a potential role of variants in interacting cilia genes in modifying clinical phenotypes.

Introduction Myasthenia gravis (MG) is considered a paraneoplastic phenomenon of thymomas in 15% of patients. Co-existence of MG with extrathymic malignancies, and an increased risk of second malignancy in patients with thymoma have been reported. Data on clinical characteristics of MG patients with extrathymic malignancies and the role of concomitant diseases and their treatment are lacking. Methods The clinical records of 188 consecutive MG patients were studied retrospectively. We examined whether gender, age, generalized disease, seropositivity for acetyl-choline receptor antibodies, occurrence of thymoma, immunosuppressive therapy and occurrence of other autoimmune diseases determined an increased risk for development of extrathymic malignancy. Results This group followed the typical epidemiological characteristics of MG. Thirty-three patients (17.6%) had a thymoma. Twenty-nine patients (15.4%) had 30 extrathymic malignant tumors of various origins. Only four patients with extrathymic tumors had an associated thymoma. Tumors were diagnosed between 20 years prior to and 35 years after the appearance of MG. Older age of MG onset was the only risk factor identified for development of malignancy in MG. Discussion Extrathymic malignancies are common in MG patients, especially in the older age group. There are no specific clinical features of the subgroup of MG patients with cancer. Although MG is not a paraneoplastic phenomenon of extrathymic malignancy, the association between MG and malignancy may be due to a common background of immune dysregulation.

The bifunctional enzyme UDP-N-acetylglucosamine-2-epimerase/N-acetylmannosamine kinase (GNE) is essential for early embryonic development and catalyzes the rate limiting step in sialic acid biosynthesis. Although epimerase and kinase activities have been attributed to GNE, little is known about the regulation, differential expression, and subcellular localization of GNE in vivo. Mutations in GNE cause a rare inherited muscle disorder in humans called hereditary inclusion body myopathy (HIBM). However, the role of GNE in HIBM pathogenesis has not been defined yet. Here, we show that the GNE protein is expressed in various mammalian cells and tissues with highest levels found in cancer cells and liver. In human skeletal muscle, GNE protein is developmentally regulated: high levels are found in immature myoblasts but low levels in mature skeletal muscle. The GNE protein colocalizes with resident proteins of the Golgi compartment in a variety of human cells including muscle. Drug-induced disruption of the Golgi and subsequent recovery reveals co-distribution of GNE along with Golgi-targeted proteins. This subcellular localization of GNE is in good agreement with its established role as the key enzyme of sialic acid biosynthesis, since the sialylation of glycoconjugates takes place in the Golgi complex. Surprisingly, GNE is also detected in the nucleus. Upon nocodazole treatment, GNE redistributes to the cytoplasm suggesting that GNE may act as a nucleocytoplasmic shuttling protein. A regulatory role for GNE shifting between the nuclear and the Golgi compartment is proposed. Further insight into GNE regulation may promote the understanding of HIBM pathogenesis.

The transthyretin Tyr77 variant of familial amyloid polyneuropathy (FAP) has been identified in a few North American and European patients, but the full spectrum of its clinical manifestations is still not known. We report a 3-generation family of Jewish-Yemenite origin with Tyr77 FAP presenting with atypical features. The affected individuals had sensorimotor and autonomic neuropathy and cardiomyopathy accompanied by prominent dysphagia, hearing loss and asymptomatic carpal tunnel syndrome. Brain MRI in the proband showed multifocal white matter lesions. These features extend the reported Tyr77 phenotype and support the modifying effect of additional factors on the disease expression.

In the paper titled “Presymptomatic Treatment with Acetylcholinesterase Antisense Oligonucleotides Prolongs Survival in ALS (G93A-SOD1) Mice,” the first and last names of all the authors were reversed. The correct names in order (first name, last name) have been shown in the front matter of the paper.

Hereditary neuropathy with liability to pressure palsies (HNPP), classically presenting as recurrent focal neuropathies precipitated by trauma or compression, is an autosomal dominant neuropathy due to a deletion at chromosomal locus 17p12. Inflammatory demyelinating polyneuropathy (IDP), a putative autoimmune disorder presenting in an acute (AIDP) or a chronic form (CIDP), has been rarely reported as familial. We present a father and two daughters of Jewish Kurdish origin who developed IDP within 10 years. The unusual familial history led us to reevaluate the diagnosis of IDP, and suggested an autosomal dominant pedigree. DNA analysis identified the deletion typical of HNPP on chromosome 17. Screening for the HNPP deletion in patients with atypical, recurrent, or familial IDP might be warranted.

The human RECK gene, mapped at 9p13→p12, is known as a tumor suppressor gene and as a key regulator of extracellular matrix integrity and angiogenesis. We have established the entire genomic structure of this gene, which spans more than 87 kb and consists of 21 exons and 20 introns, and identified thirteen single nucleotide polymorphisms (SNPs). Four SNPs were identified in the coding region of the gene (exons 1, 9, 13 and 15), and the remaining nine in introns 5, 8, 10, 12, 15 and 17. The availability of the genomic organization of the RECK gene and the identification of polymorphisms throughout its entire genome will facilitate the evaluation of its role in several disorders and also contribute to the assignment of genes to the several diseases mapped to this chromosomal region.

Laing early onset distal myopathy and myosin storage myopathy are caused by mutations of slow skeletal/β-cardiac myosin heavy chain encoded by the gene MYH7, as is a common form of familial hypertrophic/dilated cardiomyopathy. The mechanisms by which different phenotypes are produced by mutations in MYH7, even in the same region of the gene, are not known. To explore the clinical spectrum and pathobiology, we screened the MYH7 gene in 88 patients from 21 previously unpublished families presenting with distal or generalized skeletal muscle weakness, with or without cardiac involvement. Twelve novel mutations have been identified in thirteen families. In one of these families, the father of the proband was found to be a mosaic for the MYH7 mutation. In eight cases, de novo mutation appeared to have occurred, which was proven in four. The presenting complaint was footdrop, sometimes leading to delayed walking or tripping, in members of 17 families (81%), with other presentations including cardiomyopathy in infancy, generalized floppiness, and scoliosis. Cardiac involvement as well as skeletal muscle weakness was identified in nine of 21 families. Spinal involvement such as scoliosis or rigidity was identified in 12 (57%). This report widens the clinical and pathological phenotypes, and the genetics of MYH7 mutations leading to skeletal muscle diseases.

Background The syndrome of isolated progressive upper-limb distal weakness and atrophy results from disease processes affecting lower motor neurons originating in the cervical anterior horn gray matter. Lower motor neuron dysfunction restricted to the C7–T1 myotomes in the absence of neuropathy, upper motor neuron signs, sphincter disturbances or abnormality on conventional MR imaging is suggestive of either Hirayama disease (HD), or the initial manifestation of a progressive motor neuron disease such as amyotrophic lateral sclerosis (ALS). In HD the supposed etiologic mechanism is a mechanical compression of the cervical spinal cord during neck flexion; therefore, dynamic MRI (dMRI) of the cervical cord might help differentiate between these possibilities. Methods This was a multi-center observational cohort study. Over a 4-year period between 8/2009 and 8/2013, 22 patients were identified as having a disease consistent with HD. We identified a subgroup of patients suspected of suffering from active progressive disease and prospectively followed them after performing dynamic MRI studies of the cervical spine. Results Twenty-two patients were identified as having a disease consistent with HD, of whom 8 were defined as having actively progressive disease. Seven of these 8 patients demonstrated clear dynamic compression of the cervical spine during neck flexion. The patient who did not demonstrate the typical MRI changes associated with HD went on to develop generalized ALS. Conclusions dMRI has a practical role in patients presenting with progressive upper-limb distal weakness and atrophy, and the presence of characteristic changes typical of HD may suggest a more optimistic prognosis.

Post-exercise recovery of intracellular pH (pH(i)) assessed using phosphorus magnetic resonance spectroscopy has not been previously evaluated in its entirety due to its complex time-course and missing data points resulting from a transient loss of inorganic phosphate signal. By considering the transition from exercise to recovery as a step function input, pH(i) recovery was modeled based on the creatine-kinase equilibrium, and the entire pH(i) recovery was characterized by calculating the time required for pH(i) recovery (t(pHrec)). Applying this methodology, normal subjects showed a strong linear correlation between phosphocreatine (PCr) half-time and t(pHrec) (r = 0.90, P < 0.001). In mitochondrial myopathy (MM) patients with weakness in the limb examined, 9/10 had faster pH(i) recovery relative to PCr recovery; wide normal ranges from a control group which included deconditioned subjects resulted in 7 of those 10 patients having otherwise normal recovery indices. Therefore, modeling pH(i) recovery allows characterization of the entire pH(i) recovery and detects altered proton handling in MM patients, including those with otherwise normal recovery indices.

Two major entities continue to be controversial in the field of clinical myotoxicity: the various myopathies that are induced by the cholesterol-lowering agents and the acute quadriplegic myopathy of intensive care. Both conditions are relatively common, but their pathogenesis is unclear. The problematic issues related to these disorders are presented, with suggested topics for future research.

The cluster in Jews of Libyan origin of limb-girdle muscular dystrophy type 2B due to a dysferlin 1624delG mutation is described. The carrier frequency of this mutation is calculated to be approximately 10% in this population, in which the disease prevalence is at least 1 per 1300 adults. Twenty-nine patients from 12 families were all homozygous for the same mutation. However, clinical features were heterogeneous even within the same family: in half of the patients onset was in the distal muscles of the legs, which is similar to Miyoshi myopathy, while in others onset was in the proximal musculature, which is similar to other forms of limb-girdle dystrophies. Age at onset varied from 12 to 28 years (mean 20.3 +/- 5.5 years). One patient was presymptomatic at age 28 years. Progression was slow regardless of age of onset, patients remaining ambulatory until at least 33 years. Five patients described subacute, painful enlarged calves as an early, unusual feature. The variable features in this ethnic cluster contribute to the definition of the clinical spectrum of dysferlinopathies in general. The cause of the observed heterogeneity remains unclear.

Mutations in dysferlin were recently described in patients with Miyoshi myopathy, a disorder that preferentially affects the distal musculature, and in patients with Limb-Girdle Muscular Dystrophy 2B, a disorder that affects the proximal musculature. Despite the phenotypic differences, the types of mutations associated with Miyoshi myopathy and Limb-Girdle Muscular Dystrophy 2B do not differ significantly. Thus, the etiology of the phenotypic variability associated with dysferlin mutations remains unknown. Using genetic linkage and mutation analysis, we identified a large inbred pedigree of Yemenite Jewish descent with limb-girdle muscular dystrophy. The phenotype in these patients included slowly progressive, proximal, and distal muscular weakness in the lower limbs with markedly elevated serum creatine kinase (CK) levels. These patients had normal development and muscle strength and function in early life. Muscle biopsies from 4 affected patients showed a typical dystrophic pattern but interestingly, in 2, an inflammatory process was seen. The inflammatory infiltrates included primarily CD3 positive lymphocytes. Associated with this phenotype, we identified a previously undescribed frameshift mutation at nucleotide 5711 of dysferlin. This mutation produced an absence of normal dysferlin mRNA synthesis by affecting an acceptor site and cryptic splicing. Thus, splice site mutations that disrupt dysferlin may produce a phenotype associated with inflammation.

The purpose of this study was to assess the effect of physical deconditioning on skeletal muscle's oxidative metabolism as evaluated by phosphorus-31 magnetic resonance spectroscopy ((31)P MRS). Twenty-seven subjects without muscle disease, representing a wide range of fitness levels, were evaluated with (31)P MRS. Spectra were obtained at rest and during recovery from in-magnet exercise. The data show a significant correlation between maximum resting metabolic equivalent (MET) score and the following (31)P MRS recovery indices: adenosine diphosphate and phosphocreatine recovery half-time; initial phosphocreatine resynthesis rate; calculated estimation of mitochondrial capacity; pH at end of exercise; and phosphocreatine depletion. In addition, significant differences between the deconditioned and conditioned group were found for all of the aforementioned recovery indices. At rest, only the inorganic phosphate concentration was significantly different between the two groups. These data indicate that physical activity level should be taken into account when assessing patients' oxidative metabolism with (31)P MRS.

Phosphorus magnetic resonance spectroscopy (P-MRS) has now been used in the investigation of muscle energy metabolism in health and disease for over 15 years. The present review describes the basics of the metabolic observations made by P-MRS including the assumptions and problems associated with the use of this technique. Extramuscular factors, which may affect the P-MRS results, are detailed. The important P-MRS observations in patients with mitochondrial myopathies, including the monitoring of experimental therapies, are emphasized. The findings in other metabolic myopathies (those associated with glycolytic defects or endocrine disturbances) and in the destructive myopathies (the dystrophies and the inflammatory myopathies) are also described. Observations made in normal and abnormal fatigue, fibromyalgia, and malignant hyperthermia are considered. Finally, a summary of the possible diagnostic use of P-MRS in exercise intolerance is provided.

We have previously demonstrated that patients with mitochondrial myopathies can benefit from short-term aerobic exercise training. In this study, we compared the responses to short-term aerobic training of patients with mitochondrial myopathies, patients with nonmetabolic myopathies, and sedentary normal subjects. Training consisted of 8 weeks of treadmill exercise at 70% to 85% of estimated maximum heart rate reserve. All groups showed significant improvements in estimated aerobic capacity as well as heart rate and blood lactate at submaximal exercise intensities. The increase in estimated aerobic capacity was greater in the mitochondrial myopathy patients than in the other two groups. Phosphorus magnetic resonance spectroscopy demonstrated increased oxidative capacity of muscle in patients with mitochondrial myopathies in response to this training but not in patients with other, nonmetabolic myopathies or sedentary control subjects. A self-assessed measurement of functional status (SF-36) suggested improved quality of life associated with the training. This study demonstrates that short-term aerobic training at low intensity can benefit patients with nonmetabolic myopathies but to a lesser extent than patients with mitochondrial myopathies.

Recently, a single gene, DYSF, has been identified whichis mutated in patients with limb-girdle muscular dys-trophy type 2B (LGMD2B) and with Miyoshi myopathy(MM). This is of interest because these diseases havebeen considered as two distinct clinical conditions sincedifferent muscle groups are the initial targets. Dysferlin,the protein product of the gene, is a novel molecule with-out homology to any known mammalian protein. Wehave now raised a monoclonal antibody to dysferlin andreport on the expression of this new protein: immunola-belling with the antibody (designated NCL-hamlet) dem-onstrated a polypeptide of ∼230 kDa on western blots ofskeletal muscle, with localization to the muscle fibremembrane by microscopy at both the light and electronmicroscopic level. A specific loss of dysferlin labellingwas observed in patients with mutations in the LGMD2B/MM gene. Furthermore, patients with two different frame-shifting mutations demonstrated very low levels ofimmunoreactive protein in a manner reminiscent of thedystrophin expressed in many Duchenne patients.Analysis of human fetal tissue showed that dysferlin wasexpressed at the earliest stages of development exam-ined, at Carnegie stage 15 or 16 (embryonic age 5–6weeks). Dysferlin is present, therefore, at a time when thelimbs start to show regional differentiation. Lack of dys-ferlin at this critical time may contribute to the pattern ofmuscle involvement that develops later, with the onset ofa muscular dystrophy primarily affecting proximal or dis-tal muscles. INTRODUCTIONTo date, at least eight forms of autosomal recessive musculardystrophy have appeared under the general heading of limb-girdle muscular dystrophy (LGMD). These are in two groups:those with abnormal expression of the dystrophin–glycoproteincomplex ( 1) and those where labelling of proteins in this complexis unaffected. Thus, the sarcoglycanopathies (sometimes knownas LGMD types 2C, 2D, 2E and 2F) are caused by defects in thegenes for γ-, α-, β- or δ-sarcoglycan on chromosomes 13q12,17q12, 4q12 and 5q33, respectively (2–5). Among the dys-trophies where expression of the sarcoglycans is normal, the generesponsible for LGMD2A has been identified as the chromosome15q15-encoded muscle-specific protease calpain 3 (), and the6gene for LGMD2B was identified recently as the 2p13-locatedDYSF (7,8). Genes for LGMD2G and LGMD2H have beenlocalized to 17q11–q12 (9) and 9q31–q33 (10), and furtherLGMD genes are inferred ( 9,11). Although clinically heterogen-eous in terms of age of onset and rate of progression, the featurethat all these conditions share is weakness that starts with theproximal limb-girdle muscles. Unexpectedly, a disease character-ized by the early involvement of distal calf muscles, Miyoshimyopathy (MM), was shown to be caused by mutations in thesame gene as LGMD2B ( 8). Dysferlin, the protein product of theDYSF gene, is a novel molecule without homology to any knownmammalian protein. However, the gene does have significanthomology, throughout its length, to a nematode spermatogenesisfactor (fer-1), a fact that contributed to the name it was given(7,8). Here we present the first description of dysferlin proteinexpression.RESULTSDysferlin antibody generationA monoclonal antibody was developed that recognizes an epitopenear the C-terminus of dysferlin, within amino acids 1999–2016,just before the predicted transmembrane domain (7,8). Adsorp-tion with the immunizing peptide removed all immunoreactivity.Since the intention was to raise a diagnostically useful antibodythat would enable patients with LGMD2B to be identified, the

Phosphorus magnetic resonance (MR) spectroscopy was used to measure the recovery kinetics of calculated cytoplasmic metabolically active adenosine diphosphate (ADP) after exercise in normal subjects and patients with mitochondrial myopathies. These kinetics have previously been fitted with a single exponential function, despite a complex time-dependent undershoot in many subjects. By considering the transition from ischemic-exercise to perfused-recovery as a step function input, a second-order linear system was developed yielding a step response function to fit the ADP recovery. Using this method, an average improvement in fit of 23% resulted in a significant improvement in the characterization of ADP recovery for all normal subjects with substantial undershoot. The patient group had a comparable improvement in fit of 11%. Fitting the ADP recovery with a second-order step response function can provide significantly better characterization of muscle oxidative metabolism in vivo. Magn Reson Med 41:926–932, 1999. © 1999 Wiley-Liss, Inc.

The normal distribution of serum creatine kinase (CK) was determined in 428 men (mean age = 21.5) and 540 women (mean age = 20.2). The bootstrap method was employed to obtain statistical parameters of CK reference range and correlations with physical activity habits, BMI, cigarette smoking and alcohol consumption. CK distribution was non-Gaussian and skewed toward the higher values; 18.9% of the men and 4.6% of the women had values above the upper reference limits defined for the commercial assay kit. The median 97.5 percentile value was 532 u/l for men and 248 u/l for women (95% confidence interval of 384-738 u/l and 184-340 u/l, respectively). A significant correlation was found only between CK and alcohol consumption in men. Myoglobin level in a representative group of subjects correlated well with CK activity for both genders. Our findings define the range of CK values in a healthy, young, heterogeneous population. We suggest that only CK levels above the determined 97.5 percentile should warrant further clinical investigation.

Adult polyglucosan body disease (APBD) is a late-onset, slowly progressive disorder of the nervous system caused by glycogen branching enzyme (GBE) deficiency in a subgroup of patients of Ashkenazi Jewish origin. Similar biochemical finding is shared by glycogen storage disease type IV (GSD IV) that, in contrast to APBD, is an early childhood disorder with primarily systemic manifestations. Recently, the GBE cDNA was cloned and several mutations were characterized in different clinical forms of GSD IV. To examine whether mutations in the GBE gene account for APBD, we studied 7 patients from five Jewish families of Ashkenazi ancestry. The diagnosis was based on the typical clinical and pathological findings, and supported by reduced GBE activity. We found that the clinical and biochemical APBD phenotype in all five families cosegregated with the Tyr329Ser mutation, not detected in 140 controls. As this mutation was previously identified in a nonprogressive form of GSD IV and was shown in expression studies to result in a significant residual GBE activity, present findings explain the late onset and slowly progressive course of APBD in our patients. We conclude that APBD represents an allelic variant of GSD IV, but the reason for the difference in primary tissue involvement must be established.

We review the current knowledge about the genetic susceptibility to develop inflammatory inclusion body myositis, especially in relation to the increased presence of the HLA DR3 allele in patients with familial and sporadic forms, indicating an autoimmune predisposition. The main focus of the review is the clinical and genetic presentations of the various hereditary inclusion body myopathies. Criteria for diagnosis and classification of these myopathies are presented. The spectrum of the recessive forms of hereditary inclusion body myopathies currently linked to chromosome 9p1-q1 is described, with emphasis on the up-to-date status of the gene search for these forms.

The limb-girdle muscular dystrophies are a genetically heterogeneous group of inherited progressive muscle disorders that affect mainly the proximal musculature, with evidence for at least three autosomal dominant and eight autosomal recessive loci. The latter mostly involve mutations in genes encoding components of the dystrophin-associated complex; another form is caused by mutations in the gene for the muscle-specific protease calpain 3. Using a positional cloning approach, we have identified the gene for a form of limb-girdle muscular dystrophy that we previously mapped to chromosome 2p13 (LGMD2B). This gene shows no homology to any known mammalian gene, but its predicted product is related to the C. elegans spermatogenesis factor fer-1. We have identified two homozygous frameshift mutations in this gene, resulting in muscular dystrophy of either proximal or distal onset in nine families. The proposed name 'dysferlin' combines the role of the gene in producing muscular dystrophy with its C. elegans homology.