Hereditary Myopathy with Early Respiratory Failure (HMERF) is a progressive titinopathy caused by dominant missense mutations in the A-band region of TTN , a domain essential for sarcomere stability. Patients suffering with HMERF manifest muscle weakness, early respiratory involvement, and reduced life expectancy, yet no effective therapies currently exist. A major barrier has been the lack of an animal model that replicated HMERF pathology. In this study, we established the first CRISPR-Cas9 engineered mouse model of HMERF, carrying a patient-derived missense mutation in Ttn . Homozygous mutant mice exhibited a severe and uniform phenotype, including kyphosis, thoracic deformities, abnormal gait, diaphragm weakness, and premature death. Histological analysis revealed disrupted sarcomeres, abnormal myotilin accumulation, and necklace-like cytoplasmic bodies in diaphragm muscle, resembling human pathology. Multi-omics approach revealed consistent dysregulation of genes and proteins linked to muscle structure, cytoskeletal integrity, and cellular homeostasis, representing disease pathomechanisms. A major limitation of this study was the restricted availability of muscle tissue, which prevented broader analysis across multiple muscle types. Nevertheless, overlapping transcriptomic and proteomic dysregulation, including differential splicing, highlight key molecular effects driving disease progression. In conclusion, this mouse model provides mechanistic insight into HMERF and establishes a platform for evaluating therapeutic strategies. It represents an essential step toward developing targeted interventions for this rare and severe neuromuscular disorder.

The small heat shock protein HSPB6 (a.k.a. Hsp20) is highly expressed in striated and smooth muscles. It modulates the oligomerization of its paralogs HSPB1 and CRYAB (HSPB5) and is involved e.g. in cytoskeletal regulation and autophagy. While HSPB6 variants have been implicated in cardiomyopathy, they have not been previously linked to neuromuscular disease. We report here a patient with late-onset myopathy and cataract, carrying in cis the novel HSPB6 variant c.464delC and the common polymorphism c.488G > C, together resulting in the extended protein p.Pro155Argfs*25;p.Gly163Arg. The family history was consistent with dominant inheritance. The mutant protein showed decreased solubility due to phase separation propensity, and caused mislocalization of CRYAB and BAG3, and a decrease of HSPB1 in transfected cells. The patient's muscle biopsy showed rimmed vacuoles and, in line with the functional studies, accumulation of HSPB6 and its interaction partners. The identified HSPB6 variants are most likely the cause of the muscle disease in this family, thus identifying HSPB6 mutations as a novel cause of vacuolar myopathy. Other reported HSPB6 variants causing a late frameshift or extension may cause disease in a similar fashion.

Background: Titin, the largest human protein, is essential for sarcomere structure and function. The TTN gene, spanning 364 exons, undergoes extensive alternative splicing thus producing multiple isoforms. The M-band region, encoded by exons 359-364, plays a critical role in sarcomere integrity and mechanical stability. Exon 363 is of interest due to its involvement in titinopathies. Pathogenic truncating variants in this exon have been linked to recessive myopathies, including and mainly young-onset recessive distal titinopathy. Methods: A multicenter study was conducted on six patients from five unrelated families with confirmed recessive titinopathy and truncating variants in exon 363. Clinical evaluations were performed. Genetic testing and segregation analysis confirmed the phase of the variants. Results: A novel truncating variant c.107578C>T, p.(Gln35860Ter) was identified in four unrelated patients of Eastern European ancestry, all carrying a second pathogenic variant in a canonical TTN exon. These patients exhibited juvenile/young-adult onset recessive distal titinopathy with progressive lower limb weakness, frequently asymmetric muscle involvement, and no cardiac or respiratory complications. A Belgian family presented with a congenital myopathy caused by a novel frameshift deletion c.107430delA, p.(Ser35811AlafsTer32) in exon 363, in compound heterozygosity with a truncating variant in exon 208. These patients showed a more severe phenotype. Conclusions: This study expands the spectrum of TTN-related myopathies, emphasizing exon 363's pathogenic significance. Truncating exon 363 variants contribute to young onset recessive distal and sometimes early onset titinopathy with contractures, and the phenotype severity is influenced by the second variant's location and exon usage.

BACKGROUND:Variants in CASQ1, encoding a calcium-binding protein in the fast-twitch fibers of skeletal muscle, cause sarcoplasmic reticulum aberrations such as large vacuoles with CASQ1 inclusions or, less commonly, tubular aggregates. To date, seven pathogenic variants have been described, all dominant missense variants. The typical symptoms of the disease include muscle weakness, cramps, myalgia, and fatigue. METHODS:We used genome and exome sequencing to identify the disease-causing variants in two families with dominant myopathy. The candidate variants were further characterized by cell-transfection studies and western blotting. RESULTS:In Family 1, three patients presented with exercise intolerance, cramps, and myalgia. Additionally, the proband had muscle weakness and her muscle biopsy showed nemaline bodies. In electron microscopy, there were morphological changes in the triads and the SR-feet in all patients. A variant in CASQ1, p.(Glu89Lys), was found in all patients, whereas the proband had also two compound heterozygous variants in NEB. In Family 2, three patients presented with progressive muscle weakness. The proband's muscle biopsy showed marked atrophy. The frameshift variant p.(Gly383Alafs*39) in CASQ1 was found in all three patients. In silico analysis indicated that the variant results in protein extension, which was confirmed by western blotting of patient muscle. Cell-transfection studies showed that the variant protein forms aggregates. CONCLUSION:This study expands the spectrum of pathogenic CASQ1 variants. The morphological changes in the SR-feet indicate a novel pathogenetic mechanism.

Background Titin truncating variants (TTNtvs) have been repeatedly reported as causative of recessive but not dominant skeletal muscle disorders. Objective To determine whether a single heterozygous nonsense variant in TTN can be responsible for the observed dominant myopathy in a large family. Methods In this case series, all available family members (8 affected and 6 healthy) belonging to a single family showing autosomal dominant inheritance were thoroughly examined clinically and genetically. Results All affected family members showed a similar clinical phenotype with a combination of cardiac and skeletal muscle involvement. Muscle imaging data revealed titin-compatible hallmarks. Genetic analysis revealed in all affected patients a nonsense TTN variant c.70051C>T p.(Arg23351*), in exon 327. RNA sequencing confirmed the lack of complete nonsense-mediated decay, and protein studies convincingly revealed expression of a shortened titin fragment of the expected size. Discussion We conclude that a single heterozygous nonsense variant in titin occasionally can cause a dominant myopathy as shown in this large family. Therefore, monoallelic titin truncating variants should be considered as possible disease-causing variants in unsolved patients with a dominant myopathy. However, large segregation studies, muscle imaging, and RNA and protein assays are needed to support the clinical and genetic interpretation.

In digenic inheritance, pathogenic variants in two genes must be inherited together to cause disease. Only very few examples of digenic inheritance have been described in the neuromuscular disease field. Here we show that predicted deleterious variants in SRPK3 , encoding the X-linked serine/argenine protein kinase 3, lead to a progressive early onset skeletal muscle myopathy only when in combination with heterozygous variants in the TTN gene. The co-occurrence of predicted deleterious SRPK3 / TTN variants was not seen among 76,702 healthy male individuals, and statistical modeling strongly supported digenic inheritance as the best-fitting model. Furthermore, double-mutant zebrafish ( srpk3 −/− ; ttn.1 +/− ) replicated the myopathic phenotype and showed myofibrillar disorganization. Transcriptome data suggest that the interaction of srpk3 and ttn.1 in zebrafish occurs at a post-transcriptional level. We propose that digenic inheritance of deleterious changes impacting both the protein kinase SRPK3 and the giant muscle protein titin causes a skeletal myopathy and might serve as a model for other genetic diseases.

Chaperone-assisted selective autophagy (CASA) is a highly selective pathway for the disposal of misfolding and aggregating proteins. In muscle, CASA assures muscle integrity by favoring the turnover of structural components damaged by mechanical strain. In neurons, CASA promotes the removal of aggregating substrates. A crucial player of CASA is HSPB8 (heat shock protein family B (small) member 8), which acts in a complex with HSPA, their cochaperone BAG3, and the E3 ubiquitin ligase STUB1. Recently, four novel HSPB8 frameshift (fs) gene mutations have been linked to neuromyopathies, and encode carboxy-terminally mutated HSPB8, sharing a common C-terminal extension. Here, we analyzed the biochemical and functional alterations associated with the HSPB8_fs mutant proteins. We demonstrated that HSPB8_fs mutants are highly insoluble and tend to form proteinaceous aggregates in the cytoplasm. Notably, all HSPB8 frameshift mutants retain their ability to interact with CASA members but sequester them into the HSPB8-positive aggregates together with two autophagy receptors SQSTM1/p62 and TAX1BP1. This copartitioning process negatively affects the CASA capability to remove its clients and causes a general failure in proteostasis response. Further analyses revealed that the aggregation of the HSPB8_fs mutants occurs independently of the other CASA members or from the autophagy receptors interaction, but it is an intrinsic feature of the mutated amino acid sequence. HSPB8_fs mutants aggregation alters the differentiation capacity of muscle cells and impairs sarcomere organization. Collectively, these results shed light on a potential pathogenic mechanism shared by the HSPB8_fs mutants described in neuromuscular diseases.Abbreviations : ACD: α-crystallin domain; ACTN: actinin alpha; BAG3: BAG cochaperone 3; C: carboxy; CASA: chaperone-assisted selective autophagy; CE: carboxy-terminal extension; CLEM: correlative light and electron microscopy; CMT2L: Charcot-Marie-Tooth type 2L; CTR: carboxy-terminal region; dHMNII: distal hereditary motor neuropathy type II; EV: empty vector; FRA: filter retardation assay; fs: frameshift; HSPA/HSP70: heat shock protein family A (Hsp70); HSPB1/Hsp27: heat shock protein family B (small) member 1; HSPB8/Hsp22: heat shock protein family B (small) member 8; HTT: huntingtin; KO: knockout; MAP1LC3B/LC3: microtubule associated protein 1 light chain 3 beta; MD: molecular dynamics; MTOC: microtubule organizing center; MYH: myosin heavy chain; MYOG: myogenin; NBR1: NBR1 autophagy cargo receptor; CALCOCO2/NDP52: calcium binding and coiled-coil domain 2; NSC34: Neuroblastoma X Spinal Cord 34; OPTN: optineurin; polyQ: polyglutamine; SQSTM1/p62: sequestosome 1; STUB1/CHIP: STIP1 homology and U-box containing protein 1; TARDBP/TDP-43: TAR DNA binding protein; TAX1BP1: Tax1 binding protein 1; TUBA: tubulin alpha; WT: wild-type.

Recessive mutations in the DNAJB2 gene, encoding the J-domain co-chaperones DNAJB2a and DNAJB2b, have previously been reported as the genetic cause of progressive peripheral neuropathies, rarely involving pyramidal signs, parkinsonism and myopathy. We describe here a family with the first dominantly acting DNAJB2 mutation resulting in a late-onset neuromyopathy phenotype. The c.832 T > G p.(*278Glyext*83) mutation abolishes the stop codon of the DNAJB2a isoform resulting in a C-terminal extension of the protein, with no direct effect predicted on the DNAJB2b isoform of the protein. Analysis of the muscle biopsy showed reduction of both protein isoforms. In functional studies, the mutant protein mislocalized to the endoplasmic reticulum due to a transmembrane helix in the C-terminal extension. The mutant protein underwent rapid proteasomal degradation and also increased the turnover of co-expressed wild-type DNAJB2a, potentially explaining the reduced protein amount in the patient muscle tissue. In line with this dominant negative effect, both wild-type and mutant DNAJB2a were shown to form polydisperse oligomers.

Background and ObjectivesThis study aimed to characterize the phenotype of a novel myalgic myopathy encountered in a Finnish family.MethodsFour symptomatic and 3 asymptomatic individuals from 2 generations underwent clinical, neurophysiologic, imaging, and muscle biopsy examinations. Targeted sequencing of all known myopathy genes was performed.ResultsA very rare CACNA1S gene variant c.2893G>C (p.E965Q) was identified in the family. The symptomatic patients presented with exercise-induced myalgia, cramping, muscle stiffness, and fatigue and eventually developed muscle weakness. Examinations revealed mild ptosis and unusual muscle hypertrophy in the upper limbs. In the most advanced disease stage, muscle weakness and muscle atrophy of the limbs were evident. In some patients, muscle biopsy showed mild myopathic findings and creatine kinase levels were slightly elevated.DiscussionMyalgia is a very common symptom affecting quality of life. Widespread myalgia may be confused with other myalgic syndromes such as fibromyalgia. In this study, we show that variants in CACNA1S gene may be one cause of severe exercise-induced myalgia.

Rhabdomyolysis is the acute breakdown of skeletal myofibres in response to an initiating factor, most commonly toxins and over exertion. A variety of genetic disorders predispose to rhabdomyolysis through different pathogenic mechanisms, particularly in patients with recurrent episodes. However, most cases remain without a genetic diagnosis. Here we present six patients who presented with severe and recurrent rhabdomyolysis, usually with onset in the teenage years; other features included a history of myalgia and muscle cramps. We identified 10 bi-allelic loss-of-function variants in the gene encoding obscurin (OBSCN) predisposing individuals to recurrent rhabdomyolysis. We show reduced expression of OBSCN and loss of obscurin protein in patient muscle. Obscurin is proposed to be involved in sarcoplasmic reticulum function and Ca2+ handling. Patient cultured myoblasts appear more susceptible to starvation as evidenced by a greater decreased in sarcoplasmic reticulum Ca2+ content compared to control myoblasts. This likely reflects a lower efficiency when pumping Ca2+ back into the sarcoplasmic reticulum and/or a decrease in Ca2+ sarcoplasmic reticulum storage ability when metabolism is diminished. OSBCN variants have previously been associated with cardiomyopathies. None of the patients presented with a cardiomyopathy and cardiac examinations were normal in all cases in which cardiac function was assessed. There was also no history of cardiomyopathy in first degree relatives, in particular in any of the carrier parents. This cohort is relatively young, thus follow-up studies and the identification of additional cases with bi-allelic null OBSCN variants will further delineate OBSCN-related disease and the clinical course of disease.

Objective Inclusion body myositis (IBM) has an unclear molecular etiology exhibiting both characteristic inflammatory T-cell activity and rimmed-vacuolar degeneration of muscle fibers. Using in-depth gene expression and splicing studies, we aimed at understanding the different components of the molecular pathomechanisms in IBM. Methods We performed RNA-seq on RNA extracted from skeletal muscle biopsies of clinically and histopathologically defined IBM ( n = 24), tibial muscular dystrophy ( n = 6), and histopathologically normal group ( n = 9). In a comprehensive transcriptomics analysis, we analyzed the differential gene expression, differential splicing and exon usage, downstream pathway analysis, and the interplay between coding and non-coding RNAs (micro RNAs and long non-coding RNAs). Results We observe dysregulation of genes involved in calcium homeostasis, particularly affecting the T-cell activity and regulation, causing disturbed Ca 2+ -induced apoptotic pathways of T cells in IBM muscles. Additionally, LCK/p56, which is an essential gene in regulating the fate of T-cell apoptosis, shows increased expression and altered splicing usage in IBM muscles. Interpretation Our analysis provides a novel understanding of the molecular mechanisms in IBM by showing a detailed dysregulation of genes involved in calcium homeostasis and its effect on T-cell functioning in IBM muscles. Loss of T-cell regulation is hypothesized to be involved in the consistent observation of no response to immune therapies in IBM patients. Our results show that loss of apoptotic control of cytotoxic T cells could indeed be one component of their abnormal cytolytic activity in IBM muscles.

Background and Objectives To clinically, genetically, and histopathologically characterize patients presenting with an unusual combination of distal myopathy and facial weakness, without involvement of upper limb or shoulder girdle muscles. Methods Two families with a novel form of actininopathy were identified. Patients had been followed up over 10 years. Their molecular genetic diagnosis was not clear after extensive investigations, including analysis of candidate genes and FSHD1-related D4Z4 repeats. Results Patients shared a similar clinical phenotype and a common pattern of muscle involvement. They presented with a very slowly progressive myopathy involving anterior lower leg and facial muscles. Muscle MRI finding showed complete fat replacement of anterolateral compartment muscles of the lower legs with variable involvement of soleus and gastrocnemius but sparing thigh muscles. Muscle biopsy showed internalized nuclei, myofibrillar disorganization, and rimmed vacuoles. High-throughput sequencing identified in each proband a heterozygous single nucleotide deletion (c.2558del and c.2567del) in the last exon of the ACTN2 gene. The deletions are predicted to lead to a novel but unstructured slightly extended C-terminal amino acid sequence. Discussion Our findings indicate an unusual form of actininopathy with specific molecular and clinical features. Actininopathy should be considered in the differential diagnosis of distal myopathy combined with facial weakness.

BACKGROUND AND OBJECTIVES:To determine the genetic cause of the disease in the previously reported family with adult-onset autosomal dominant distal myopathy (myopathy, distal, 3; MPD3).METHODS:Continued clinical evaluation including muscle MRI and muscle pathology. A linkage analysis with single nucleotide polymorphism arrays and genome sequencing were used to identify the genetic defect, which was verified by Sanger sequencing. RNA sequencing was used to investigate the transcriptional effects of the identified genetic defect.RESULTS:Small hand muscles (intrinsic, thenar, and hypothenar) were first involved with spread to the lower legs and later proximal muscles. Dystrophic changes with rimmed vacuoles and cytoplasmic inclusions were observed in muscle biopsies at advanced stage. A single nucleotide polymorphism array confirmed the previous microsatellite-based linkage to 8p22-q11 and 12q13-q22. Genome sequencing of three affected family members combined with structural variant calling revealed a small heterozygous deletion of 160 base pairs spanning the second last exon 10 of the heterogeneous nuclear ribonucleoprotein A1 (HNRNPA1) gene, which is in the linked region on chromosome 12. Segregation of the mutation with the disease was confirmed by Sanger sequencing. RNA sequencing showed that the mutant allele produces a shorter mutant mRNA transcript compared with the wild-type allele. Immunofluorescence studies on muscle biopsies revealed small p62 and larger TDP-43 inclusions.DISCUSSION:A small exon 10 deletion in the gene HNRNPA1 was identified as the cause of MPD3 in this family. The new HNRNPA1-related phenotype, upper limb presenting distal myopathy, was thus confirmed, and the family displays the complexities of gene identification.

Heterogeneous nuclear ribonucleoproteins are RNA-binding proteins, many of which contain low complexity sequences known as 'prion-like domains' or PrLDs. Mutations in these PrLDs are associated with several diseases such as Multisystem proteinopathies (MSP) and Amyotrophic lateral sclerosis (ALS). These mutations affect the abnormal stress granule (SG) formation and clearance resulting in increased toxicity due to aggregated proteins. Understanding how mutations in heterogenous nuclear ribonuclearprotein A1 (HNRNPA1) functionally affect the SGs, holds the key in improving our knowledge of the molecular pathomechanisms of the disease. We identified three different mutations in the PrLD of HNRNPA1 (NM_031157) associated with dominant myopathy phenotypes in three unrelated families (FAM1-3). In FAM1, the previously reported D314N mutation segregated with a proximal rimmed vacuolar myopathy. The finding was initially missed due to coverage issues in exomes and traditional variant calling on captured regions. In FAM2, published earlier with a distinct distal myopathy phenotype (MPD3), we performed linkage analysis, subsequent Sanger sequencing of candidate genes, exome and genome sequencing (GS), which remained inconclusive. Copy Number Variant analysis of newer high depth GS identified a heterozygous 160 bp deletion in exon 10 of HNRNPA1 in the linked region, segregating with the phenotype in this family. The finding again asserted the possible coverage issues plaguing this gene. In FAM3 with severe myopathic atrophy in forearms and hands, we identified a de novo heterozygous indel in the same exon 10 causing extension of the HNRNPA1 tail by 3 amino acids. We are currently investigating the effects of these mutations on transcript and protein level. We postulate that different mutations in the PrLD of HNRNPA1 can give rise to different overlapping phenotypes. Our internal analysis of over 400 exomes and genomes suggests that due to the genomic complexity of this region, some sequencing chemistries do not result in high confidence coverage. The coverage analysis of data from 11,230 samples in Solve-RD suggests that exome capture kits have difficulty in covering the GC rich regions of HNRNPA1 which could lead to cases of 'missed diagnosis'.

We report the first mosaic mutation, a deletion of exons 11-107, identified in the nebulin gene in a Finnish patient presenting with a predominantly distal congenital myopathy and asymmetric muscle weakness. The female patient is ambulant and currently 26 years old. Muscle biopsies showed myopathic features with type 1 fibre predominance, strikingly hypotrophic type 2 fibres and central nuclei, but no nemaline bodies. The deletion was detected in a copy number variation analysis based on next-generation sequencing data. The parents of the patient did not carry the deletion. Mosaicism was detected using a custom, targeted comparative genomic hybridisation array. Expression of the truncated allele, less than half the size of full-length nebulin, was confirmed by Western blotting. The clinical and histological picture resembled that of a family with a slightly smaller deletion, and that in patients with recessively inherited distal forms of nebulin-caused myopathy. Asymmetry, however, was a novel feature. (c) 2021 Elsevier B.V. All rights reserved.

Using deep phenotyping and high-throughput sequencing, we have identified a novel type of distal myopathy caused by mutations in the Small muscle protein X-linked ( SMPX ) gene. Four different missense mutations were identified in ten patients from nine families in five different countries, suggesting that this disease could be prevalent in other populations as well. Haplotype analysis of patients with similar ancestry revealed two different founder mutations in Southern Europe and France, indicating that the prevalence in these populations may be higher. In our study all patients presented with highly similar clinical features: adult-onset, usually distal more than proximal limb muscle weakness, slowly progressing over decades with preserved walking. Lower limb muscle imaging showed a characteristic pattern of muscle involvement and fatty degeneration. Histopathological and electron microscopic analysis of patient muscle biopsies revealed myopathic findings with rimmed vacuoles and the presence of sarcoplasmic inclusions, some with amyloid-like characteristics. In silico predictions and subsequent cell culture studies showed that the missense mutations increase aggregation propensity of the SMPX protein. In cell culture studies, overexpressed SMPX localized to stress granules and slowed down their clearance.

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Distal myopathies are genetic primary muscle disorders with a prominent weakness at onset in hands and/or feet. The age of onset (from early childhood to adulthood), the distribution of muscle weakness (upper versus lower limbs) and the histological findings (ranging from nonspecific myopathic changes to myofibrillar disarrays and rimmed vacuoles) are extremely variable. However, despite being characterized by a wide clinical and genetic heterogeneity, the distal myopathies are a category of muscular dystrophies: genetic diseases with progressive loss of muscle fibers. Myopathic congenital arthrogryposis is also a form of distal myopathy usually caused by focal amyoplasia. Massive parallel sequencing has further expanded the long list of genes associated with a distal myopathy, and contributed identifying as distal myopathy-causative rare variants in genes more often related with other skeletal or cardiac muscle diseases. Currently, almost 20 genes (ACTN2, CAV3, CRYAB, DNAJB6, DNM2, FLNC, HNRNPA1, HSPB8, KHLH9, LDB3, MATR3, MB, MYOT, PLIN4, TIA1, VCP, NOTCH2NLC, LRP12, GIPS1) have been associated with an autosomal dominant form of distal myopathy. Pathogenic changes in four genes (ADSSL, ANO5, DYSF, GNE) cause an autosomal recessive form; and disease-causing variants in five genes (DES, MYH7, NEB, RYR1 and TTN) result either in a dominant or in a recessive distal myopathy. Finally, a digenic mechanism, underlying a Welander-like form of distal myopathy, has been recently elucidated. Rare pathogenic mutations in SQSTM1, previously identified with a bone disease (Paget disease), unexpectedly cause a distal myopathy when combined with a common polymorphism in TIA1. The present review aims at describing the genetic basis of distal myopathy and at summarizing the clinical features of the different forms described so far.

Eight patients from five families with undiagnosed dominant distal myopathy underwent clinical, neurophysiological and muscle biopsy examinations. Molecular genetic studies were performed using targeted sequencing of all known myopathy genes followed by segregation of the identified mutations in the affected families using Sanger sequencing. Two novel mutations in DNAJB6 J domain, c.149C>T (p.A50V) and c.161A>C (p.E54A), were identified as the cause of disease. The muscle involvement with p.A50V was distal calf-predominant, and the p.E54A was more proximo-distal. Histological findings were similar to those previously reported in DNAJB6 myopathy. In line with reported pathogenic mutations in the glycine/phenylalanine (G/F) domain of DNAJB6, both the novel mutations showed reduced anti-aggregation capacity by filter trap assay and TDP-43 disaggregation assays. Modeling of the protein showed close proximity of the mutated residues with the G/F domain. Myopathy-causing mutations in DNAJB6 are not only located in the G/F domain, but also in the J domain. The identified mutations in the J domain cause dominant distal and proximo-distal myopathy, confirming that mutations in DNAJB6 should be considered in distal myopathy cases.