Clinical and Molecular Spectrum Associated with COL6A3 c.7447A>G p.(Lys2483Glu) Variant: Elucidating its Role in Collagen VI-related Myopathies.

BACKGROUND: Dominant and recessive autosomal pathogenic variants in the three major genes (COL6A1-A2-A3) encoding the extracellular matrix protein collagen VI underlie a group of myopathies ranging from early-onset severe conditions (Ullrich congenital muscular dystrophy) to milder forms maintaining independent ambulation (Bethlem myopathy). Diagnosis is based on the combination of clinical presentation, muscle MRI, muscle biopsy, analysis of collagen VI secretion, and COL6A1-A2-A3 genetic analysis, the interpretation of which can be challenging. OBJECTIVE: To refine the phenotypical spectrum associated with the frequent COL6A3 missense variant c.7447A>G (p.Lys2483Glu). METHODS: We report the clinical and molecular findings in 16 patients: 12 patients carrying this variant in compound heterozygosity with another COL6A3 variant, and four homozygous patients. RESULTS: Patients carrying this variant in compound heterozygosity with a truncating COL6A3 variant exhibit a phenotype consistent with COL6-related myopathies (COL6-RM), with joint contractures, proximal weakness and skin abnormalities. All remain ambulant in adulthood and only three have mild respiratory involvement. Most show typical muscle MRI findings. In five patients, reduced collagen VI secretion was observed in skin fibroblasts cultures. All tested parents were unaffected heterozygous carriers. Conversely, two out of four homozygous patients did not present with the classical COL6-RM clinical and imaging findings. Collagen VI immunolabelling on cultured fibroblasts revealed rather normal secretion in one and reduced secretion in another. Muscle biopsy from one homozygous patient showed myofibrillar disorganization and rimmed vacuoles. CONCLUSIONS: In light of our results, we postulate that the COL6A3 variant c.7447A>G may act as a modulator of the clinical phenotype. Thus, in patients with a typical COL6-RM phenotype, a second variant must be thoroughly searched for, while for patients with atypical phenotypes further investigations should be conducted to exclude alternative causes. This works expands the clinical and molecular spectrum of COLVI-related myopathies.

Clinical guide for the diagnosis and follow-up of myotonic dystrophy type 1, MD1 or Steinert's disease. / Guía clínica para el diagnóstico y seguimiento de la distrofia miotónica tipo 1, DM1 o enfermedad de Steinert.

BACKGROUND AND OBJECTIVES: Steinert's disease or myotonic dystrophy type 1 (MD1), (OMIM 160900), is the most prevalent myopathy in adults. It is a multisystemic disorder with dysfunction of virtually all organs and tissues and a great phenotypical variability, which implies that it has to be addressed by different specialities with experience in the disease. The knowledge of the disease and its management has changed dramatically in recent years. This guide tries to establish recommendations for the diagnosis, prognosis, follow-up and treatment of the complications of MD1. MATERIAL AND METHODS: Consensus guide developed through a multidisciplinary approach with a systematic literature review. Neurologists, pulmonologists, cardiologists, endocrinologists, neuropaediatricians and geneticists have participated in the guide. RECOMMENDATIONS: The genetic diagnosis should quantify the number of CTG repetitions. MD1 patients need cardiac and respiratory lifetime follow-up. Before any surgery under general anaesthesia, a respiratory evaluation must be done. Dysphagia must be screened periodically. Genetic counselling must be offered to patients and relatives. CONCLUSION: MD1 is a multisystemic disease that requires specialised multidisciplinary follow-up.

Implication of the SH3TC2 gene in Charcot-Marie-Tooth disease associated with deafness and/or scoliosis: Illustration with four new pathogenic variants.

The autosomal recessive demyelinating form of Charcot-Marie-Tooth can be due to SH3TC2 gene pathogenic variants (CMT4C, AR-CMTde-SH3TC2). We report on a series of 13 patients with AR-CMTde-SH3TC2 among a French cohort of 350 patients suffering from all type of inheritance peripheral neuropathy. The SH3TC2 gene appeared to be the most frequently mutated gene for demyelinating neuropathy in this series by NGS. Four new pathogenic variants have been identified: two nonsense variants (p.(Tyr970*), p.(Trp1199*)) and two missense variants (p.(Leu1126Pro), p.(Ala1206Asp)). The recurrent variant p.Arg954* was present in 62%, and seems to be a founder mutation. The phenotype is fairly homogeneous, as all these patients, except the youngest ones, presented scoliosis and/or hearing loss.

Development and validation of a motor function classification in patients with neuromuscular disease: the NM-score.

OBJECTIVE: To develop a classification for neuromuscular disease patients in each of the three motor function domains (D1: standing and transfers; D2: axial and proximal function; D3: distal function). MATERIALS AND METHODS: A draft classification was developed by a study group and then improved by qualitative validation studies (according to the Delphi method) and quantitative validation studies (content validity, criterion validity and inter-rater reliability). A total of 448 patients with genetic neuromuscular diseases participated in the studies. RESULTS: On average, it took 6.3minutes to rate a patient. The inter-rater agreement was good when the classification was based on patient observation or an interview with the patient (Cohen's kappa=0.770, 0.690 and 0.642 for NM-Score D1, D2 and D3 domains, respectively). Stronger correlations (according to Spearman's coefficient) with the respective "gold standard" classifications were found for NM-Score D1 (0.86 vs. the Vignos Scale and -0.88 vs. the Motor Function Measure [MFM]-D1) and NM-Score D2 (-0.7 vs. the Brooke Scale and 0.64 vs. MFM D2) than for NM-Score D3 (0.49 vs. the Brooke scale and -0.49 vs. MFM D3). DISCUSSION/CONCLUSIONS: The NM-Score is a reliable, reproducible outcome measure with value in clinical practice and in clinical research for the description of patients and the constitution of uniform patient groups (in terms of motor function).

Relief from episodic weakness with pyridostigmine in paramyotonia congenita: a family study.

Pyridostigmine relieved episodic weakness in a family with paramyotonia congenita resulting from the R1448C mutation in the sodium channel gene. The transmission was autosomal dominant and the patients had paradoxical myotonia and exercise-induced weakness. On electrophysiological studies there were myotonic potentials, and there was progressive reduction of compound muscle action potential (CMAP) amplitudes after short exercise associated with clinical weakness. Pyridostigmine in doses of 60 mg three times daily abolished the drop in the postexercise CMAP amplitude and reduced the amplitude decrement to slow rate repetitive stimulation, but there continued to be a drop in amplitude on exposure to cold. The decline of the CMAP amplitude on exposure to cold was controlled by treatment with phenytoin. The clinical and electrophysiological features are discussed in relation to therapy with pyridostigmine and phenytoin.

Carrier frequency of SMA by quantitative analysis of the SMN1 deletion in the Iranian population.

BACKGROUND AND PURPOSE: Spinal muscular atrophy (SMA) is a common autosomal recessive neuromuscular disorder. Carrier frequency studies of SMA have been reported for various populations. Although no large-scale population-based studies of SMA have been performed in Iran, previous estimates have indicated that the incidence of autosomal recessive disorder partly because of the high prevalence of consanguineous marriage is much higher in the Iranian population than in other populations. METHODS: In this study, we used a reliable and highly sensitive quantitative real-time PCR assay with SYBR green I dye to detect the copy number of the SMN1 gene to determine the carrier frequency of SMA in 200 healthy unrelated, non-consanguineous couples from different part of Iran. RESULTS: To validate the method in our samples, we determined the relative quantification (RQ) of patients with homozygous deletion (0.00) and hemyzygous carriers (0.29-0.55). The RQ in 10 of 200 normal individuals were within the carrier range of 0.31-0.57, estimating a carrier frequency of 5% in the Iranian population. CONCLUSIONS: Our data show that the SMA carrier frequency in Iran is higher than in the European population and that further programs of population carrier detection and prenatal testing should be implemented.

Transcriptional explorations of CAPN3 identify novel splicing mutations, a large-sized genomic deletion and evidence for messenger RNA decay.

Mutations in the gene encoding calpain-3 (CAPN3) cause autosomal recessive limb-girdle muscular dystrophy type 2A (LGMD2A) and idiopathic eosinophilic myositis. Accurate diagnosis and genetic counselling are based on the identification of disease-causing mutations on both alleles of CAPN3 in the patients. In the present study, we used transcriptional analysis as a complementary approach for patients suspected of being affected with LGMD2A, in whom initial denaturing high-performance liquid chromatography genomic mutation screening evidenced no or only one CAPN3 mutation obviously considered as disease causing. This allowed to identify and characterize cDNA deletions. Further genomic analysis allowed to determine the origin of these deletions, either as splicing defects caused by intronic mutations or as an internal multi-exonic deletion. In particular, we report two novel CAPN3 mutations (c.1745 + 4_1745 + 7delAGTG in IVS13 and c.2185-16A>G in IVS20) and a recurrent large-sized genomic deletion including exons 2-8 for which genomic breakpoints have been characterized. In addition, our results indicate nonsense-mediated messenger RNA decay as a mechanism for under-expression of CAPN3 associated to some specific variations.

'Cap myopathy': case report of a family.

We report the observation of an 18-year-old girl, whose clinical presentation was very suggestive of a congenital myopathy with neonatal onset. A congenital myopathy had been already diagnosed in her brother and in addition her half-cousin died diagnosed with a severe nemaline myopathy at age 4 years. A muscle biopsy performed on both siblings revealed histological and ultrastructural features of 'cap myopathy'. This case report suggests that 'cap myopathy' and some cases of nemaline myopathy with neonatal onset might be two phenotypic expressions of the same genetic disorder. These two entities could therefore, perhaps, be regarded as 'Z-line disorders' possibly caused by defective myofibrillogenesis.

LGMD2A: genotype-phenotype correlations based on a large mutational survey on the calpain 3 gene.

We present here the clinical, molecular and biochemical findings from 238 limb-girdle muscular dystrophy type 2A (LGMD2A) patients, representing approximately 50% (238 out of 484) of the suspected calpainopathy cases referred for the molecular study of the calpain 3 (CAPN3) gene. The mean age at onset of LGMD2A patients was approximately 14 years, and the first symptoms occurred between 6 and 18 years of age in 71% of patients. The mean age at which the patients became wheelchair bound was 32.2 years, with 84% requiring the use of a wheelchair between the age of 21 and 40 years. There was no correlation between the age at onset and the time at which the patient became wheelchair bound, nor between the sex of the patient and the risk of becoming wheelchair bound. Of the cases where the CAPN3 gene was not affected, approximately 20% were diagnosed as LGMD2I muscular dystrophy, while facioscapulohumeral muscular dystrophy (FSHD) was uncommon in this sample. We identified 105 different mutations in the CAPN3 gene of which 50 have not been described previously. These were distributed throughout the coding region of the gene, although some exons remained free of mutations. The most frequent mutation was 2362AG-->TCATCT (exon 22), which was present in 30.7% of the chromosomes analysed (146 chromosomes). Other recurrent mutations described were N50S, 550DeltaA, G222R, IVS6-1G-->A, A483D, IVS17+1G-->T, 2069-2070DeltaAC, R748Q and R748X, each of which was found in >5 chromosomes. The type of mutation in the CAPN3 gene does not appear to be a risk factor for becoming dependent on a wheelchair at a determined age. However, in the cases with two null mutations, there were significantly fewer patients that were able to walk than in the group of patients with at least one missense mutation. Despite the fact that the results of phenotyping and western blot might be biased due to multiple referral centres, producing a diagnosis on the basis of the classical phenotype is neither sufficiently sensitive (86.7%) nor specific (69.3%), although western blot proved to be even less sensitive (52.5%) yet more specific (87.8%). In this case LGMD2I was a relevant cause of false-positive diagnoses. Considering both the clinical phenotype and the biochemical information together, the probability of correctly diagnosing a calpainopathy is very high (90.8%). However, if one of the analyses is lacking, the probability varies from 78.3 to 73.7% depending on the information available. When both tests are negative, the probability that the sample comes from a patient with LGMD2A was 12.2%.

Non-collagenic etiologies of muscle weakness with joint deformities: about two paradigmatic case reports.

Muscle weakness associated to marked joint deformities is not an uncommon clinical situation in daily neuromuscular clinics. These abnormalities encompass a large variety of conditions including non-primary muscle disorders. Besides well-defined and rather readily recognisable hereditary syndromes such as Bethlem myopathy or Ullrich congenital muscular dystrophy, some unusual etiologies should also be considered. We report here two paradigmatic cases in which we found mutations in two novel genes corresponding to two newly described entities (progressive pseudorheumatoid dysplasia, PPD, and infantile systemic hyalinosis, ISH) both conditions in which the clinical picture can mimick primary muscle disease.

Clinical and histologic findings in autosomal centronuclear myopathy.

Centronuclear myopathy (CNM) is a congenital myopathy characterized by chains of centrally located nuclei in a large number of muscle fibers. Clinically, an early-onset form was reported in several autosomal-recessive (AR) families and many sporadic patients, whereas a late-onset form was found in most autosomal-dominant (AD) families. The boundary between these two forms remains unclear, and the molecular basis of autosomal CNM is still unresolved. To better define the clinical and morphologic characteristics of autosomal CNM, the authors analyzed a series of 29 patients from 12 families. Two subgroups were identified in three AD families: two families had a relatively late onset of disease and a slow progression of diffuse weakness, whereas the third family, who had a similar clinical course, also presented a unique diffuse muscle hypertrophy. Two presumed AR families and seven sporadic patients were analyzed together, and three subgroups were identified: 1) an early-onset form with ophthalmoparesis; 2) an early-onset form without ophthalmoparesis; and 3) a late-onset form without ophthalmoparesis. Overall, 23 muscle biopsies were reviewed; a majority of patients had >20% central nuclei, fiber type 1 predominance, and a radial distribution of sarcoplasmic strands on oxidative stains. A marked endomysial fibrosis was observed in three sporadic patients with a relatively severe clinical course. The classification reported in this study will be useful for the diagnosis and the follow-up evaluation of patients with autosomal CNM and for the research into the molecular defects underlying the condition.

[Oculopharyngeal muscular dystrophy: study of patients from seven Spanish families with different GCG expansions in PABP2 gene]. / Distrofia muscular oculofaríngea: estudio de pacientes pertenecientes a siete familias españolas con diferentes expansiones GCG en el gen PABP2.

INTRODUCTION: Autosomal dominant oculopharyngeal muscular dystrophy (OPMD), with late onset due to ptosis and/or dysphagia, is caused by short (GCG)8-13 triplet-repeat expansions in the polyadenylation binding protein 2 (PABP2) gene, which is localized in chromosome 14q11. The severity of the dominant OPMD as well as the number of expansions that cause the disease are variable. (GCG)9 is mentioned as the most frequent and the genotype/phenotype has still not been well-determined. OBJECTIVE: To describe the type of expansions (GCG)n found in Spanish families with OPMD, establishing if there is variability of them and the possible geno-phenotypical correlations. METHODS: Clinicopathological and molecular studies have been performed in 15 consecutive patients, belonging to seven Spanish families with OPMD. The muscular biopsy study under electronmicroscopy shows intranuclear inclusions (INIs) in all the examined patients (one patient per family). The genetic findings confirm the cause of the disease in all the affected members and in one clinically asymptomatic member of one recently examined family: three families (six, one and one studied members, respectively) present the (GCG)9 expansion, two families (one studied member each one) present the (GCG)10 expansion and two families (one and four studied members respectively) present the (GCG)11 expansion. In these 15 patients with a short GCG expansion causing OPMD, clinical tests for OPMD and a follow-up study of their clinical course have been carefully assessed: in patients with the (GCG)9 expansion major abnormalities appeared in extrinsic ocular mobility and more precocious presentation of limb girld (lumbopelvic preferentially) weakness leading to a great disability before the seventh decade of life under the seventies in some patients and sometimes leading to death. In patients with (GCG)10 and (GCG)11 expansions, eye movements are always preserved and the limb girld muscles weakness did not appear before the seventh decade. No correlation seems to exist between age of onset of the ptosis or dysphagia and the different (GCG)n expansions and the surgical treatment of ptosis, performed in eight patients, showed good results independently of the (GCG)n mutation. CONCLUSIONS: Although further clinical and genetic studies are necessary to establish a strict genotype/phenotype correlation in OPMD, we concluded that the (GCG)9 expansion involve more severe phenotypes than those related to the (GCG)10 or (GCG)11 expansions. Therefore, genetic testing could benefit prognosis in asymptomatic individuals.

[Recent progress in pediatric neurological rehabilitation]. / Quoi de neuf en rééducation neurologique infantile?

New challenges in rehabilitation for children with neurological diseases directly depend on advances made in medical research and on the quality of the environment. This is relevant to motor function as a whole, to new therapeutic avenues in spasticity, to global approaches in the evaluation of cognitive and learning disabilities, as well as curative perspectives in neuromuscular disease. Networking with the family and other actors in the environmental field is essential to achieve a better social integration. A true collaboration between physicians and pediatricians is necessary to work toward more progress.

Genomic organization of the dysferlin gene and novel mutations in Miyoshi myopathy.

OBJECTIVE: Mutations in the skeletal muscle gene dysferlin cause two autosomal recessive forms of muscular dystrophy: Miyoshi myopathy (MM) and limb girdle muscular dystrophy type 2B (LGMD2B). The purpose of this study was to define the genomic organization of the dysferlin gene and conduct mutational screening and a survey of clinical features in 21 patients with defined molecular defects in the dysferlin gene. METHODS: Genomic organization of the gene was determined by comparing the dysferlin cDNA and genomic sequence in P1-derived artificial chromosomes (PACs) containing the gene. Mutational screening entailed conformational analysis and sequencing of genomic DNA and cDNA. Clinical records of patients with defined dysferlin gene defects were reviewed retrospectively. RESULTS: The dysferlin gene encompasses 55 exons spanning over 150 kb of genomic DNA. Mutational screening revealed nine novel mutations associated with MM. The range of onset in this patient group was narrow with a mean of 19.0 +/- 3.9 years. CONCLUSION: This study confirms that the dysferlin gene is mutated in MM and LGMD2B and extends understanding of the timing of onset of the disease. Knowledge of the genomic organization of the gene will facilitate mutation detection and investigations of the molecular biologic properties of the dysferlin gene.

Pseudo-metabolic presentation in a Duchenne muscular dystrophy symptomatic carrier with 'de novo' duplication of dystrophin gene.

We report a 6-year-old female patient presenting with a sudden and severe single episode of rhabdomyolysis in which screening for a metabolic disorder was negative. Four months after the episode a muscle biopsy was performed and showed a mild pattern of necrosis/regeneration. Upon immunofluorescence, a mosaic pattern of dystrophin deficiency was found, and in the dystrophin deficient muscle fibres, the four proteins of the sarcoglycan complex were also lacking. Genetic analysis showed a duplication of exons 3 to 17 on one X-chromosome of the proband, but not on the mother's X-chromosome. A clearly skewed X-inactivation (85% of the defective X being active) was found and is consistent with the patient being symptomatic. To our knowledge, a spontaneous rhabdomyolysis in a female Duchenne muscular dystrophy carrier has never been reported.