Best practice guidelines on genetic diagnostics of facioscapulohumeral muscular dystrophy: Update of the 2012 guidelines.

The gold standard for facioscapulohumeral muscular dystrophy (FSHD) genetic diagnostic procedures was published in 2012. With the increasing complexity of the genetics of FSHD1 and 2, the increase of genetic testing centers, and the start of clinical trials for FSHD, it is crucial to provide an update on our knowledge of the genetic features of the FSHD loci and renew the international consensus on the molecular testing recommendations. To this end, members of the FSHD European Trial Network summarized the evidence presented during the 2022 ENMC meeting on Genetic diagnosis, clinical outcome measures, and biomarkers. The working group additionally invited genetic and clinical experts from the USA, India, Japan, Australia, South-Africa, and Brazil to provide a global perspective. Six virtual meetings were organized to reach consensus on the minimal requirements for genetic confirmation of FSHD1 and FSHD2. Here, we present the clinical and genetic features of FSHD, specific features of FSHD1 and FSHD2, pros and cons of established and new technologies (Southern blot in combination with either linear or pulsed-field gel electrophoresis, molecular combing, optical genome mapping, FSHD2 methylation analysis and FSHD2 genotyping), the possibilities and challenges of prenatal testing, including pre-implantation genetic testing, and the minimal requirements and recommendations for genetic confirmation of FSHD1 and FSHD2. This consensus is expected to contribute to current clinical management and trial-readiness for FSHD.

Recurrent de-novo gain-of-function mutation in SPTLC2 confirms dysregulated sphingolipid production to cause juvenile amyotrophic lateral sclerosis.

BACKGROUND: Amyotrophic lateral sclerosis (ALS) leads to paralysis and death by progressive degeneration of motor neurons. Recently, specific gain-of-function mutations in SPTLC1 were identified in patients with juvenile form of ALS. SPTLC2 encodes the second catalytic subunit of the serine-palmitoyltransferase (SPT) complex. METHODS: We used the GENESIS platform to screen 700 ALS whole-genome and whole-exome data sets for variants in SPTLC2. The de-novo status was confirmed by Sanger sequencing. Sphingolipidomics was performed using liquid chromatography and high-resolution mass spectrometry. RESULTS: Two unrelated patients presented with early-onset progressive proximal and distal muscle weakness, oral fasciculations, and pyramidal signs. Both patients carried the novel de-novo SPTLC2 mutation, c.203T>G, p.Met68Arg. This variant lies within a single short transmembrane domain of SPTLC2, suggesting that the mutation renders the SPT complex irresponsive to regulation through ORMDL3. Confirming this hypothesis, ceramide and complex sphingolipid levels were significantly increased in patient plasma. Accordingly, excessive sphingolipid production was shown in mutant-expressing human embryonic kindney (HEK) cells. CONCLUSIONS: Specific gain-of-function mutations in both core subunits affect the homoeostatic control of SPT. SPTLC2 represents a new Mendelian ALS gene, highlighting a key role of dysregulated sphingolipid synthesis in the pathogenesis of juvenile ALS. Given the direct interaction of SPTLC1 and SPTLC2, this knowledge might open new therapeutic avenues for motor neuron diseases.

Clinical and genetic characteristics of Emery-Dreifuss muscular dystrophy patients from Turkey: 30 years longitudinal follow-up study.

Emery-Dreifuss muscular dystrophy (EDMD) is a rare inherited disorder usually presenting in childhood with early contractures, slowly progressive scapulohumeroperoneal weakness/atrophy and potentially fatal dilated cardiomyopathy with conduction defects. We evaluated clinical and genetic findings of 32 patients with EDMD phenotype from 14 unrelated families, diagnosed at the Department of Neurology, Istanbul Faculty of Medicine between 1989 and 2022. Twenty-three patients from 8 unrelated families were diagnosed with EDMD1 (58%), 5 patients from 3 families with EDMD2 (21%), and 2 patients from 1 family with the rare EDMD3 (7%). Genetic diagnosis was achieved in 12 unrelated kinships with classical EDMD phenotype (86%) by applying panel testing, but no mutation could be determined in 2 patients with classical EDMD phenotype from 2 unrelated families (14%). Three novel pathogenic variants (c.19delC, c.416_417delTT, c.123C > G) in EMD, and a novel (c.1441dupT) heterozygous likely pathogenic variant in LMNA gene were found. This is the largest cohort from Turkey, expanding the genetic spectrum of EDMD, and providing clues for genetic testing of EDMD in Turkey.

The clinical use of impulse oscillometry in neuromuscular diseases.

BACKGROUND: The patients with neuromuscular diseases (NMD) are very fragile and it is hard to evaluate respiratory involvement of the primary disease in this group. Therefore, our study aimed to reveal the relationship between pulmonary function tests (PFT) and impulse oscillometry (IOS) and their correlation with respiratory clinical findings in NMD. MATERIAL AND METHODS: A total of 86 consecutive patients with NMD were included. The clinical findings of respiratory involvement, PFT, and IOS results of the patients were analyzed. RESULTS: Forty patients out of 86 were female. There were 29 patients with amyotrophic lateral sclerosis, four patients with myasthenia gravis, and 53 patients with muscular dystrophies/myopathies. According to the PFT results, 47 patients had restrictive PFT. However, there was no difference in IOS parameters when we compared the patients according to restrictions in PFT. A positive correlation was found with FVC %pred and X5. PEF %pred values were positively correlated with X10, X15, and X20, and negatively correlated with AX and R5-20. The patients with worse swallowing capability had increased Rrs levels, and more negative Xrs levels. The shortness of breath led to lower FEV1 %pred., higher R5, AX and R5-20, and also more negative X10, X15, and X35. CONCLUSION: Clinically reported dysphagia, a decreased capability of coughing, and shortness of breath in patients with NMD make Rrs increase in general, but Xrs parameters, which mainly express rib cage elasticity, turn more negative. In patients with NMD, IOS monitoring may help in evaluating the regression in respiratory functions, however, future studies are needed to understand more.

Lumbar Spinal Stenosis: A Rare Presentation of Hereditary Transthyretin Amyloidosis.

Hereditary transthyretin amyloidosis (hATTR) is caused by the mutations of the transthyretin (TTR) gene. Length dependent sensory-motor neuropathy with autonomic involvement is the hallmark of the disease. However, it can manifest with unusual phenotypes. A 53-year-old man presented with progressive weakness in lower limbs and operated for lumbar spinal stenosis. The progression of weakness restarted after two years with the addition of symptoms related to polyneuropathy. Electrodiagnostic studies revealed sensorimotor polyneuropathy with autonomic involvement. Sural nerve biopsy disclosed amyloid deposits. Genetic testing of TTR gene identified Glu89Gln mutation. Two years after the diagnosis, he had another decompressive surgery for lumbar spinal stenosis. Histopathological examination of ligamentum flavum specimens revealed amyloid deposits. During the follow up, he was diagnosed with laryngeal amyloidosis, which is an unusual manifestation. Seven years after the diagnosis, he died due to cardiac complications. Our patient suggested that hATTR with Glu89Gln may present with atypical symptoms. Clinicians should carefully look for hATTR in recurrent lumbar stenosis.

The Complex Genetic Landscape of Hereditary Ataxias in Turkey and Implications in Clinical Practice.

BACKGROUND: The genetic and epidemiological features of hereditary ataxias have been reported in several populations; however, Turkey is still unexplored. Due to high consanguinity, recessive ataxias are more common in Turkey than in Western European populations. OBJECTIVE: To identify the prevalence and genetic structure of hereditary ataxias in the Turkish population. METHODS: Our cohort consisted of 1296 index cases and 324 affected family members. Polymerase chain reaction followed by Sanger sequencing or fragment analysis were performed to screen for the trinucleotide repeat expansions in families with a dominant inheritance pattern, as well as in sporadic cases. The expansion in the frataxin (FXN) gene was tested in all autosomal recessive cases and in sporadic cases with a compatible phenotype. Whole-exome sequencing was applied to 251 probands, selected based on the family history, age of onset, and phenotype. RESULTS: Mutations in known ataxia genes were identified in 30% of 1296 probands. Friedreich's ataxia was found to be the most common recessive ataxia in Turkey, followed by autosomal recessive spastic ataxia of Charlevoix-Saguenay. Spinocerebellar ataxia types 2 and 1 were the most common dominant ataxias. Whole-exome sequencing was performed in 251 probands with an approximate diagnostic yield of 50%. Forty-eight novel variants were found in a plethora of genes, suggesting a high heterogeneity. Variants of unknown significance were discussed in light of clinical data. CONCLUSION: With the large sample size recruited across the country, we consider that our results provide an accurate picture of the frequency of hereditary ataxias in Turkey. © 2021 International Parkinson and Movement Disorder Society.

Creation and implementation of a European registry for patients with McArdle disease and other muscle glycogenoses (EUROMAC registry).

BACKGROUND: International patient registries are of particular importance for rare disorders, as they may contribute to overcome the lack of knowledge derived from low number of patients and limited awareness of these diseases, and help to learn more about their geographical or population-based specificities, which is relevant for research purposes and for promoting better standards of care and diagnosis. Our objective was to create and implement a European registry for patients with McArdle disease and other muscle glycogenoses (EUROMAC) and to disseminate the knowledge of these disorders. RESULTS: Teams from nine different countries (United Kingdom, Spain, Italy, France, Germany, Denmark, Greece, Turkey and USA) created a consortium that developed the first European registry dedicated to rare muscle glycogenoses. A work plan was implemented to design the database and platform that constitute the registry, by choosing clinical, genetics and molecular variables of interest, based on experience gained from previous national registries for similar metabolic disorders. Among dissemination activities, several teaching events were organized in different countries, especially those where the consortium considered the awareness of these diseases needs to be promoted among health professionals and patients. CONCLUSION: EUROMAC represents a step forward in the knowledge of those disorders to which it is dedicated, and will have relevant clinical outcomes at the diagnostic, epidemiological, clinical and research level.

Revisiting the complex architecture of ALS in Turkey: Expanding genotypes, shared phenotypes, molecular networks, and a public variant database.

The last decade has proven that amyotrophic lateral sclerosis (ALS) is clinically and genetically heterogeneous, and that the genetic component in sporadic cases might be stronger than expected. This study investigates 1,200 patients to revisit ALS in the ethnically heterogeneous yet inbred Turkish population. Familial ALS (fALS) accounts for 20% of our cases. The rates of consanguinity are 30% in fALS and 23% in sporadic ALS (sALS). Major ALS genes explained the disease cause in only 35% of fALS, as compared with ~70% in Europe and North America. Whole exome sequencing resulted in a discovery rate of 42% (53/127). Whole genome analyses in 623 sALS cases and 142 population controls, sequenced within Project MinE, revealed well-established fALS gene variants, solidifying the concept of incomplete penetrance in ALS. Genome-wide association studies (GWAS) with whole genome sequencing data did not indicate a new risk locus. Coupling GWAS with a coexpression network of disease-associated candidates, points to a significant enrichment for cell cycle- and division-related genes. Within this network, literature text-mining highlights DECR1, ATL1, HDAC2, GEMIN4, and HNRNPA3 as important genes. Finally, information on ALS-related gene variants in the Turkish cohort sequenced within Project MinE was compiled in the GeNDAL variant browser (www.gendal.org).

A novel shoulder disability staging system for scapulothoracic arthrodesis in patients with facioscapulohumeral dystrophy.

BACKGROUND: Scapulothoracic arthrodesis (STA) is a well-established surgical technique to provide scapular stabilisation in patients with facioscapulohumeral dystrophy (FSHD). There is no staging or scoring systems available to guide surgical decision. The aim of this study was to develop a staging system to evaluate the shoulder disability in patients with FSHD to guide surgical decision-making and assess its reliability among surgeons. METHODS: Fifty-seven shoulders of 29 patients (15 male, 14 female) with an average age of 34.5 years (13-73) were included. Six stages of the disease were defined to create a system consisting of shoulder elevation, deltoid function and scapular winging. Patients were assessed by two independent orthopaedic surgeons who were blind to each other. Statistical analyses included mean and standard deviation for descriptive variables, Pearson's correlation and Cohen's Kappa for inter- and intraobserver agreement. RESULTS: Measurement of elevation showed excellent correlation in both inter- and intraobserver assessment. There was substantial agreement on deltoid function and moderate agreement on scapular winging. Decisions on stage showed excellent agreement on interobserver and substantial agreement on intraobserver assessment. Surgical decision using the stage showed excellent agreement on both inter- and intraobserver assessment. CONCLUSION: This novel staging system has an excellent inter observer agreement on FSHD patients' shoulder disability. This would provide surgeons a beneficial tool to define patient groups that would have negatively or positively affected from STA.

Clinical exome sequencing in neuromuscular diseases: an experience from Turkey.

Neuromuscular diseases (NMDs) encompass a variety of ailments from muscular dystrophies to ataxias, in the course of which the functioning of the muscles is eventually either directly or indirectly impaired. The clinical diagnosis of a particular NMD is not always straightforward due to the clinical and genetic heterogeneity of the disorders under investigation. Traditional diagnostic tools such as electrophysiological tests and muscle biopsies are both invasive and painful methods, causing the patients to be reluctant. Next-generation sequencing, on the other hand, emerged as an alternative method for the diagnosis of NMDs, both with its minimally invasive nature and fast processing period. In this study, clinical exome sequencing (CES) was applied to a cohort of 70 probands in Turkey, 44 of whom received a final diagnosis, representing a diagnostic rate of 62.9%. Out of the 50 mutations identified to be causal, 26 were novel in the known 27 NMD genes. Two probands had complex/blended phenotypes. Molecular confirmation of clinical diagnosis of NMDs has a major prognostic impact and is crucial for the management and the possibility of alternative reproductive options. CES, which has been increasingly adopted to diagnose single-gene disorders, is also a powerful tool for revealing the etiopathogenesis in complex/blended phenotypes, as observed in two probands of the cohort.

Giant cell myositis and myocarditis revisited.

Giant cell myositis (GCMm) and giant cell myocarditis (GCMc) are two rare autoimmune conditions. Among these, GCMc is a life-threatening disease with a 1-year mortality rate of 70%. Lethal ventricular arrhythmias, rapid evolution to heart failure and sudden death risk makes GCMc an emergency condition. It is thought to be mediated by T-cells and characterized by the presence of myofiber necrosis and giant cells in biopsies. Most commonly co-manifesting conditions with GCMm and/or GCMc are thymoma, myasthenia gravis and orbital myositis, all of which are treatable. As suspicion is the key approach in diagnosis, the physician following patients with thymoma with or without myasthenia gravis and with orbital myositis should always be alert. The fatal nature of GCMc associated with these relatively benign diseases deserves a special emergency attention with prompt institution of combined immunosuppressive treatment and very early inclusion of heart failure teams.

Functional Outcomes and Complications Following Scapulothoracic Arthrodesis in Patients with Facioscapulohumeral Dystrophy.

BACKGROUND: Facioscapulohumeral dystrophy (FSHD) is an autosomal-dominant myopathy characterized by facial and shoulder girdle muscle weakness with scapular winging. Scapulothoracic arthrodesis is a successful treatment approach for patients with <90° of shoulder elevation. The purpose of the present study was to assess functional outcomes and complications following scapulothoracic arthrodesis in patients with FSHD. METHODS: We retrospectively reviewed the records of 40 patients (64 shoulders) in whom scapulothoracic arthrodesis was performed. To achieve fusion, multiple multifilament cables were used together with autologous bone and allograft bone. Preoperative and postoperative shoulder elevation and abduction; Disabilities of the Arm, Shoulder and Hand (Quick version, qDASH) scores; and pulmonary function were compared. Recorded complications were classified as pulmonary or scapular. RESULTS: The mean age of the patients at the time of the operation was 25.4 years (range, 15 to 60 years), and the mean duration of follow-up was 71.2 months (range, 12 to 185 months). When the preoperative values were compared with those at the latest follow-up, significant improvement was noted in terms of elevation (from a mean [and standard deviation] of 60.6° ± 17.2° to 123.7° ± 26.7°; p < 0.001), abduction (from 52.7° ± 15.8° to 98.8° ± 20.3°; p < 0.001), and qDASH scores (from 34.7 ± 11.4 to 13.3 ± 13.1; p < 0.001). The overall complication rate was 26.6%. There were 7 pulmonary complications (4 pneumothoraxes, 2 pleural effusions, and 1 major atelectasis), and 5 chest tube placements were required. Ten complications (including 3 rib fractures, 1 brachial plexus palsy, 2 cases of implant irritation, 2 nonunions, 1 delayed union, and 1 scapular fracture) were related to the scapular fixation, and 7 revision procedures were required. Scapulothoracic fusion was achieved in all patients but 1, who had a scapular fracture. Pulmonary function tests were performed for 19 patients, and no difference was observed between preoperative and postoperative results. CONCLUSIONS: Scapulothoracic arthrodesis with use of multifilament cables is a successful surgical technique with high fusion rates and low morbidity. Pulmonary complications are common but resolve with careful attention. LEVEL OF EVIDENCE: Therapeutic Level IV. See Instructions for Authors for a complete description of levels of evidence.

Late-onset generalized myasthenia gravis: clinical features, treatment, and outcome.

Late-onset myasthenia gravis (LOMG) is a unique MG subgroup. More information is needed on its subgroups such as non-thymomatous generalized LOMG. We evaluated the effect of demographic, clinical, and serological factors as well as different immunosuppressive modalities on outcome in generalized non-thymomatous LOMG with onset ≥ 50 years. Myasthenia Gravis Foundation of America (MGFA) Clinical Classification, MGFA postintervention score (MGFA PIS) and MG Composite scores were obtained to define the severity of disease and clinical outcome. In 95 patients with generalized non-thymomatous LOMG, 60 (63%) were men, 45 (47%) had mild disease, 80 (84%) were anti-AChR, and 56 (61%) were anti-titin positive. In those who received immunosuppressives and provided the clinical scores (84 patients), 50 (60%) had favorable outcome (MGFA PIS categories of complete stable remission, pharmacological remission and minimal manifestations) at the end of 3 years. Use of prednisone + azathioprine had significantly positive effect on outcome. The presence of anti-titin antibodies had no significant effect on severity and outcome. Five anti-MuSK-positive patients had favorable outcome. In conclusion, the presence of neither anti-titin nor anti-MuSK antibodies points to unfavorable outcome. Prednisone and azathioprine combination has beneficial effects in non-thymomatous generalized LOMG.

A multidisciplinary clinical approach to facioscapulohumeral muscular dystrophy.

BACKGROUND AND PURPOSE: Impaired shoulder function is the most disabling problem for daily life of Fascioscapulohumeral muscular dystrophy (FSHD) patients. Scapulothoracic arthrodesis can give a high impact to the functionality of patients. Here we report our experience with scapulothoracic arthrodesis and spinal stenosis surgery in FSHD patients. METHODS: 32 FSHD patients were collected between 2015-2016. Demographical and clinical features were documented. All the patients were neurologically examined. The Medical Research Council (MRC) and the FSHD evaluation scale was used to assess muscle involvement1. Scapulothoracic arthrodesis and spinal stenosis surgeries were performed in eligible patients. RESULTS: There were 16 male and 16 female (mean age 34.4 years; range 12-73) patients. 6 shoulders of 4 patients aged between 2132 years underwent scapulothoracic arthrodesis (two bilateral, one left and one right sided). Only one 63 years old female patient with severe hyperlordosis had spinal fusion surgery. All of the patients undergoing these corrective surgeries have better functionality in daily life, as well as superior shoulder elevation. CONCLUSION: Until the emergence and clinical use of novel therapeutics, surgical interventions are indicated in carefully selected patients with FSHD to improve arm movements, the posture and the quality of life of patients in general. Scapulothorosic arthrodesis is a management with good clinical results and patient satisfaction. In selected cases other corrective orthopedic surgeries like spinal fusion may also be considered.

A database for screening and registering late onset Pompe disease in Turkey.

The aim of this study was to search for the frequency of late onset Pompe disease (LOPD) among patients who had a myopathy with unknown diagnosis registered in the pre-diagnostic part of a novel registry for LOPD within a collaborative study of neurologists working throughout Turkey. Included in the study were 350 patients older than 18 years who have a myopathic syndrome without a proven diagnosis by serum creatine kinase (CK) levels, electrodiagnostic studies, and/or muscle pathology, and/or genetic tests for myopathies other than LOPD. Acid alpha glucosidase (GAA) in dried blood spot was measured in each patient at two different university laboratories. LOPD was confirmed by mutation analysis in patients with decreased GAA levels from either both or one of the laboratories. Pre-diagnostic data, recorded by 45 investigators from 32 centers on 350 patients revealed low GAA levels in a total of 21 patients; from both laboratories in 6 and from either one of the laboratories in 15. Among them, genetic testing proved LOPD in 3 of 6 patients and 1 of 15 patients with decreased GAA levels from both or one of the laboratories respectively. Registry was transferred to Turkish Neurological Association after completion of the study for possible future use and development. Our collaborative study enabled collection of a considerable amount of data on the registry in a short time. GAA levels by dried blood spot even from two different laboratories in the same patient may not prove LOPD. LOPD seemed to be rarer in Turkey than in Europe.

Congenital myasthenic syndromes in Turkey: Clinical clues and prognosis with long term follow-up.

Congenital myasthenic syndromes (CMS) are a group of hereditary disorders affecting the neuromuscular junction. Here, we present clinical, electrophysiological and genetic findings of 69 patients from 51 unrelated kinships from Turkey. Genetic tests of 60 patients were performed at Mayo Clinic. Median follow-up time was 9.8 years (range 1-22 years). The most common CMS was primary acetylcholine receptor (AChR) deficiency (31/51) and the most common mutations in AChR were c.1219 + 2T > G (12/51) and c.1327delG (6/51) in CHRNE. Four of our 5 kinships with AChE deficiency carried p.W148X that truncates the collagen domain of COLQ, and was previously reported only in patients from Turkey. These were followed by GFPT1 deficiency (4/51), DOK7 deficiency (3/51), slow channel CMS (3/51), fast channel CMS (3/51), choline acetyltransferase deficiency (1/51) and a CMS associated with desmin deficiency (1/51). Distribution of muscle weakness was sometimes useful in giving a clue to the CMS subtype. Presence of repetitive compound muscle action potentials pointed to AChE deficiency or slow channel CMS. Our experience confirms that one needs to be cautious using pyridostigmine, since it can worsen some types of CMS. Ephedrine/salbutamol were very effective in AChE and DOK7 deficiencies and were useful as adjuncts in other types of CMS. Long follow-up gave us a chance to assess progression of the disease, and to witness 12 mainly uneventful pregnancies in 8 patients. In this study, we describe some new phenotypes and detail the clinical features of the well-known CMS.

Myophosphorylase (PYGM) mutations determined by next generation sequencing in a cohort from Turkey with McArdle disease.

This study aimed to identify PYGM mutations in patients with McArdle disease from Turkey by next generation sequencing (NGS). Genomic DNA was extracted from the blood of the McArdle patients (n = 67) and unrelated healthy volunteers (n = 53). The PYGM gene was sequenced with NGS and the observed mutations were validated by direct Sanger sequencing. A diagnostic algorithm was developed for patients with suspected McArdle disease. A total of 16 deleterious PYGM mutations were identified, of which 5 were novel, including 1 splice-site donor, 1 frame-shift, and 3 non-synonymous variants. The p.Met1Val (27-patients/11-families) was the most common PYGM mutation, followed by p.Arg576* (6/4), c.1827+7A>G (5/4), c.772+2_3delTG (5/3), p.Phe710del (4/2), p.Lys754Asnfs (2/1), and p.Arg50* (1/1). A molecular diagnostic flowchart is proposed for the McArdle patients in Turkey, covering the 6 most common PYGM mutations found in Turkey as well as the most common mutation in Europe. The diagnostic algorithm may alleviate the need for muscle biopsies in 77.6% of future patients. A prevalence of any of the mutations to a geographical region in Turkey was not identified. Furthermore, the NGS approach to sequence the entire PYGM gene was successful in detecting a common missense mutation and discovering novel mutations in this population study.

Neuromuscular endplate pathology in recessive desminopathies: Lessons from man and mice.

OBJECTIVE: To assess the clinical, genetic, and myopathologic findings in 2 cousins with lack of desmin, the response to salbutamol in one patient, and the neuromuscular endplate pathology in a knock-in mouse model for recessive desminopathy. METHODS: We performed clinical investigations in the patients, genetic studies for linkage mapping, exome sequencing, and qPCR for transcript quantification, assessment of efficacy of (3-month oral) salbutamol administration by muscle strength assessment, 6-minute walking test (6MWT), and forced vital capacity, analysis of neuromuscular endplate pathology in a homozygous R349P desmin knock-in mouse by immunofluorescence staining of the hind limb muscles, and quantitative 3D morphometry and expression studies of acetylcholine receptor genes by quantitative PCR. RESULTS: Both patients had infantile-onset weakness and fatigability, facial weakness with bilateral ptosis and ophthalmoparesis, generalized muscle weakness, and a decremental response over 10% on repetitive nerve stimulation. Salbutamol improved 6MWT and subjective motor function in the treated patient. Genetic analysis revealed previously unreported novel homozygous truncating desmin mutation c.345dupC leading to protein truncation and consequent fast degradation of the mutant mRNA. In the recessive desminopathy mouse with low expression of the mutant desmin protein, we demonstrated fragmented motor endplates with increased surface areas, volumes, and fluorescence intensities in conjunction with increased α and γ acetylcholine receptor subunit expression in oxidative soleus muscle. CONCLUSIONS: The patients were desmin-null and had myopathy, cardiomyopathy, and a congenital myasthenic syndrome. The data from man and mouse demonstrate that the complete lack as well as the markedly decreased expression of mutant R349P desmin impair the structural and functional integrity of neuromuscular endplates.

Genetic heterogeneity within the HLA region in three distinct clinical subgroups of myasthenia gravis.

This study aims to investigate genetic susceptibility to early-onset and late-onset anti-acetylcholine receptor antibody positive myasthenia gravis (EOMG and LOMG) and anti-muscle specific kinase antibody positive MG (MuSK-MG) at genome-wide level in a single population. Using a custom-designed array and imputing additional variants and the classical HLA alleles in 398 patients, we detected distinct associations. In EOMG, rs113519545 in the HLA class I region (OR=5.71 [3.77-8.66], P=2.24×10(-16)), HLA-B*08:01 (OR=7.04 [3.95-12.52], P=3.34×10(-11)) and HLA-C*07:01 (OR=2.74 [1.97-3.81], P=2.07(-9)), in LOMG, rs111256513 in the HLA class II region (OR=2.22 [1.59-3.09], P=2.48×10(-6)) and in MuSK-MG, an intronic variant within HLA-DQB1 (rs68081734, OR=5.86, P=2.25×10(-14)) and HLA-DQB1*05:02 (OR=8.56, P=6.88×10(-13)) revealed the most significant associations for genome-wide significance. Differential genetic susceptibility within the HLA to EOMG, LOMG and MuSK-MG has been established in a population from Turkey.