Autosomal Recessive Dystrophy Research Articles

Can we differentiate patients with dysferlinopathies and inflammatory myopathies by ultrasound? A discriminant analysis study.

Idiopathic inflammatory myopathies (IIM) are a heterogeneous group of diseases that are characterized by inflammation and muscle weakness. Dysferlinopathies are autosomal recessive limb-girdle muscular dystrophies caused by mutations in DYSF, which share a similar clinical presentation and histopathological inflammatory changes. To determine the sonographic differences between dysferlinopathies and IIM and whether these differences allow their classification. This observational, cross-sectional, and analytical study evaluated 20 muscles from 11 patients with dysferlinopathies and 11 patients with IIM. The patients were matched for age, sex, and disease duration. Clinical and laboratory variables were analyzed. Semi-quantitative scales were used to weigh the gray scale and power Doppler muscle abnormalities. Descriptive statistics were computed and discriminant analysis was performed to determine the ultrasound variables that best predicted the final diagnosis. Forty muscles were evaluated. Atrophy and higher Heckmatt scale scores were observed in patients with dysferlinopathies. A set of three muscles (biceps/brachialis, quadriceps, and gastrocnemius) had a diagnostic accuracy of 100% (sensitivity, 100%; specificity, 100%; canonical coefficient, 0.733 p < 0.001). A set of two formulas was used to classify both diseases correctly. In the present study, scanning of three muscle groups showed high diagnostic accuracy in differentiating dysferlinopathies from MII. Ultrasound can be used as an initial test in patients with suspected muscle disease or as an additional tool to support diagnosis in controversial cases.

Knockdown of INPP5K compromises the differentiation of N2A cells.

Inositol polyphosphate 5-phosphatase K (INPP5K), also known as SKIP (skeletal muscle and kidney-enriched inositol phosphatase), is a cytoplasmic enzyme with 5-phosphatase activity toward phosphoinositides (PIs). Mutations in INPP5K are associated with autosomal recessive congenital muscular dystrophy with cataracts and intellectual disability (MDCCAID). Notably, muscular dystrophy is characterized by the hypoglycosylation of dystroglycan. Thus, far, the underlying mechanisms are only partially understood. In this study, we show that INPP5K expression increases during brain development. Knockdown of INPP5K in the neuroblastoma-derived cell line N2A impaired their neuronal-like differentiation and interfered with protein glycosylation.

Altered expression of proteins involved in metabolism in LGMDR1 muscle is lost in cell culture conditions

BackgroundLimb-girdle muscular dystrophy R1 calpain 3-related (LGMDR1) is an autosomal recessive muscular dystrophy due to mutations in the CAPN3 gene. While the pathophysiology of this disease has not been clearly established yet, Wnt and mTOR signaling pathways impairment in LGMDR1 muscles has been reported.ResultsA reduction in Akt phosphorylation ratio and upregulated expression of proteins implicated in glycolysis (HK-II) and in fructose and lactate transport (GLUT5 and MCT1) in LGMDR1 muscle was observed. In vitro analysis to establish mitochondrial and glycolytic functions of primary cultures were performed, however, no differences between control and patients were observed. Additionally, gene expression analysis showed a lack of correlation between primary myoblasts/myotubes and LGMDR1 muscle while skin fibroblasts and CD56− cells showed a slightly better correlation with muscle. FRZB gene was upregulated in all the analyzed cell types (except in myoblasts).ConclusionsProteins implicated in metabolism are deregulated in LGMDR1 patients’ muscle. Obtained results evidence the limited usefulness of primary myoblasts/myotubes for LGMDR1 gene expression and metabolic studies. However, since FRZB is the only gene that showed upregulation in all the analyzed cell types it is suggested its role as a key regulator of the pathophysiology of the LGMDR1 muscle fiber. The Wnt signaling pathway inactivation, secondary to FRZB upregulation, and GLUT5 overexpression may participate in the impaired adipogenesis in LGMD1R patients.

Single-centre experience with autosomal recessive limb-girdle muscular dystrophy: case series and literature review.

Limb-girdle muscular dystrophy (LGMD) is a group of myopathies that lead to progressive muscle weakness, predominantly involving the shoulder and pelvic girdles; it has a heterogeneous genetic etiology, with variation in the prevalence of subtypes according to the ethnic backgrounds and geographic origins of the populations. The aim of the present study was to analyze a series of patients with autosomal recessive LGMD (LGMD-R) to contribute to a better characterization of the disease and to find the relative proportion of the different subtypes in a Southern Brazil cohort. The sample population consisted of 36 patients with LGMD-R. A 9-gene targeted next-generation sequencing panel revealed variants in 23 patients with LGMD (64%), and it identified calpainopathy (LGMD-R1) in 26%, dysferlinopathy (LGMD-R2) in 26%, sarcoglycanopathies (LGMD-R3-R5) in 13%, telethoninopathy (LGMD-R7) in 18%, dystroglicanopathy (LGMD-R9) in 13%, and anoctaminopathy (LGMD-R12) in 4% of the patients. In these 23 patients with LGMD, there were 27 different disease-related variants in the ANO5, CAPN3, DYSF, FKRP, SGCA, SGCB, SGCG, and TCAP genes. There were different causal variants in different exons of these genes, except for the TCAP gene, for which all patients carried the p.Gln53* variant, and the FKRP gene, which showed recurrence of the p.Leu276Ile variant. We analyzed the phenotypic, genotypic and muscle immunohistochemical features of this Southern Brazilian cohort.

Identification of a shared, common haplotype segregating with an SGCB c.544 T > G mutation in Indian patients affected with sarcoglycanopathy

Sarcoglycanopathy is the most frequent form of autosomal recessive limb-girdle muscular dystrophies caused by mutations in SGCB gene encoding beta-sarcoglycan proteins. In this study, we describe a shared, common haplotype co-segregating in 14 sarcoglycanopathy cases from 13 unrelated families from south Indian region with the likely pathogenic homozygous mutation c.544 T > G (p.Thr182Pro) in SGCB. Haplotype was reconstructed based on 10 polymorphic markers surrounding the c.544 T > G mutation in the cases and related family members as well as 150 unrelated controls from Indian populations using PLINK1.9. We identified haplotype H1 = G, A, G, T, G, G, A, C, T, G, T at a significantly higher frequency in cases compared to related controls and unrelated control Indian population. Upon segregation analysis within the family pedigrees, H1 is observed to co-segregate with c.544 T > G in a homozygous state in all the pedigrees of cases except one indicating a probable event of founder effect. Furthermore, Identical-by-descent and inbreeding coefficient analysis revealed relatedness among 33 new pairs of seemingly unrelated individuals from sarcoglycanopathy cohort and a higher proportion of homozygous markers, thereby indicating common ancestry. Since all these patients are from the south Indian region, we suggest this region to be a primary target of mutation screening in patients diagnosed with sarcoglycanopathy.

Disease modeling and gene correction of LGMDR21 iPSCs elucidates the role of POGLUT1 in skeletal muscle maintenance, regeneration, and the satellite cell niche

Autosomal recessive limb-girdle muscular dystrophy 21 (LGMDR21) is caused by pathogenic variants in protein O-glucosyltransferase 1 (POGLUT1), which is responsible for O-glucosylation of specific epidermal growth factor (EGF) repeats found in ∼50 mammalian proteins, including Notch receptors. Previous data from patient biopsies indicated that impaired Notch signaling, reduction of muscle stem cells, and accelerated differentiation are probably involved in disease etiopathology. Using patient induced pluripotent stem cells (iPSCs), their corrected isotypes, and control iPSCs, gene expression profiling indicated dysregulation of POGLUT1, NOTCH, muscle development, extracellular matrix (ECM), cell adhesion, and migration as involved pathways. They also exhibited reduced invitro POGLUT1 enzymatic activity and NOTCH signaling as well as defective myogenesis, proliferation, migration and differentiation. Furthermore, invivo studies demonstrated significant reductions in engraftment, muscle stem cell formation, PAX7 expression, and maintenance, along with an increased percentage of mislocalized PAX7+ cells in the interstitial space. Gene correction in patient iPSCs using CRISPR-Cas9 nickase led to the rescue of the maininvitro and invivo phenotypes. These results demonstrate the efficacy of iPSCs and gene correction in disease modeling and rescue of the phenotypes and provide evidence of the involvement of muscle stem cell niche localization, PAX7 expression, and cell migration as possible mechanisms in LGMDR21.

Anaesthesia for a child with α-dystroglycan-related congenital muscular dystrophy

α-Dystroglycanopathy is a newly emerging subcategory of autosomal recessive inherited muscular dystrophies which encompasses a wide spectrum of clinical severity. Mutation of at least 18 genes which are responsible for O-mannose glycosylation of α-dystroglycan has been linked to these congenital muscular dystrophy phenotypes. α-Dystroglycan-related congenital muscular dystrophy (αDG-CMD), which may be associated with multisystem involvement, poses a challenge in perioperative management. Yet, there is a dearth of resources available for reference. We report successful anaesthesia for a 6-year-old child with αDG-CMD who underwent bilateral hamstring lengthening, left Achilles tendon lengthening, and above-the-knee fibreglass for bilateral hamstring tightness. Anaesthesia was performed using total intravenous anaesthesia (TIVA) without muscle relaxant. Bilateral sciatic nerve blocks were performed for postoperative pain control, allowing opioid-free analgesia. The patient was extubated at the end of the surgery. Perioperative considerations in αDG-CMD include anticipation of difficult airway, maintenance of thermoregulation and precautions against malignant hyperthermia with the employment of TIVA, techniques that avoid opioids and neuromuscular blocking agents (particularly suxamethonium), as well as minimizing the risk of aspiration and of raised intracranial pressure.

Exome Sequencing Identifies a Novel SGCA Gene Mutation in an Iranian Family with Limb Girdle Muscular Dystrophy: A Case Report

Introduction: Autosomal recessive limb-girdle muscular dystrophy (LGMD) is a rare congenital muscular dystrophy type. This inherited disease is one of the most common diseases resulting in severe physical health problems for infants. Genetic studies have shown that several gene mutations cause limb-girdle muscular dystrophy. This study aimed to report the case of a 10-year-old boy from an Iranian consanguineous family diagnosed with congenital muscular dystrophy and a causative genetic abnormality. Case Presentation: In this report, whole exome sequencing (WES) followed by Sanger sequencing was performed to diagnose the possible genetic defects in patients with LGMD. A novel homozygous disease-causing SGCA gene mutation (p.A107fs:c.319-329del) was found in exon 10 (NM_000023.4). Both parents were heterozygous for the detected mutation. Conclusions: It was concluded that the identified SGCA gene mutation was a pathogenic variant causing autosomal recessive LGMD.

The clinical features and TCAP mutation spectrum in a Chinese cohort of patients with limb-girdle muscular dystrophy R7.

Limb-girdle muscular dystrophy R7 (LGMDR7) is an autosomal recessive hereditary muscular dystrophy caused by mutations in titin-cap (TCAP). Here, we summarized the clinical characteristics and TCAP mutations in a Chinese cohort of 30 patients with LGMDR7. The onset age of Chinese patients was 19.89 ± 6.70years old, which is later than European and South Asian patients (P < 0.05). Clinically speaking, 20.0% of patients presented with predominant distal weakness, and 73.3% of patients presented with predominant pelvic girdle weakness. Radiological study revealed semitendinosus and magnus adductor were severely involved in Chinese LGMDR7 patients. Rectus femoris, vastus lateralis, vastus intermedius, soleus and tibialis anterior were moderately to severely involved. The most prevalent mutation in this cohort is c.26_33dupAGGTGTCG, while c.165dupG and c.110 + 5G > A are unique in Chinese population as two of the common mutations. Besides, variant c.26_33dupAGGGTGTCG might be a founder mutation in Asian patients. Internal nuclei, lobulated fibers, and scattered rimmed vacuoles were typical morphological changes in Chinese LGMDR7 patients. This is the largest LGMDR7 cohort in the Chinese population and in the world. This article also expands the clinical, pathological, mutational and radiological spectrum of patients with LGMDR7 in China and in the world.

A Dysferlin Exon 32 Nonsense Mutant Mouse Model Shows Pathological Signs of Dysferlinopathy.

Dysferlinopathies are a group of autosomal recessive muscular dystrophies caused by pathogenic variants in the DYSF gene. While several animal models of dysferlinopathy have been developed, most of them involve major disruptions of the Dysf gene locus that are not optimal for studying human dysferlinopathy, which is often caused by single nucleotide substitutions. In this study, the authors describe a new murine model of dysferlinopathy that carries a nonsense mutation in Dysf exon 32, which has been identified in several patients with dysferlinopathy. This mouse model, called Dysf p.Y1159X/p.Y1159X, displays several molecular, histological, and functional defects observed in dysferlinopathy patients and other published mouse models. This mutant mouse model is expected to be useful for testing various therapeutic approaches such as termination codon readthrough, pharmacological approaches, and exon skipping. Therefore, the data presented in this study strongly support the use of this animal model for the development of preclinical strategies for the treatment of dysferlinopathies.

Large Region of Homozygous (ROH) Identified in Indian Patients with Autosomal Recessive Limb-Girdle Muscular Dystrophy with p.Thr182Pro Variant in SGCB Gene

The sarcoglycanopathies are autosomal recessive limb-girdle muscular dystrophies (LGMDs) caused by the mutations in genes encoding the α, β, γ, and δ proteins which stabilizes the sarcolemma of muscle cells. The clinical phenotype is characterized by progressive proximal muscle weakness with childhood onset. Muscle biopsy findings are diagnostic in confirming dystrophic changes and deficiency of one or more sarcoglycan proteins. In this study, we summarized 1,046 LGMD patients for which a precise diagnosis was identified using targeted sequencing. The most frequent phenotypes identified in the patients are LGMDR1 (19.7%), LGMDR4 (19.0%), LGMDR2 (17.5%), and MMD1 (14.5%). Among the reported genes, each of CAPN3, SGCB, and DYSF variants was reported in more than 10% of our study cohort. The most common variant SGCB p.Thr182Pro was identified in 146 (12.5%) of the LGMD patients, and in 97.9% of these patients, the variant was found to be homozygous. To understand the genetic structure of the patients carrying SGCB p.Thr182Pro, we genotyped 68 LGMD patients using a whole genome microarray. Analysis of the array data identified a large ~1 Mb region of homozygosity (ROH) (chr4:51817441-528499552) suggestive of a shared genomic region overlapping the recurrent missense variant and shared across all 68 patients. Haplotype analysis identified 133 marker haplotypes that were present in ~85.3% of the probands as a double allele and absent in all random controls. We also identified 5 markers (rs1910739, rs6852236, rs13122418, rs13353646, and rs6554360) which were present in a significantly higher proportion in the patients compared to random control set ( n = 128 ) and the population database. Of note, admixture analysis was suggestive of greater proportion of West Eurasian/European ancestry as compared to random controls. Haplotype analysis and frequency in the population database indicate a probable event of founder effect. Further systematic study is needed to identify the communities and regions where the SGCB p.Thr182Pro variant is observed in higher proportions. After identifying these communities and//or region, a screening program is needed to identify carriers and provide them counselling.

Editors' Note: Prospective Natural History Study in 24 Adult Patients With LGMDR12 Over 2 Years of Follow-up: Quantitative MRI and Clinical Outcome Measures.

De Wel et al. prospectively studied 24 patients with autosomal recessive limb-girdle muscular dystrophy type 12 (LGMDR12). Patients with LGMDR12 had no appreciable clinical worsening over a 2-year period according to repeated standardized clinical assessments, such as the 6-minute walk distance, 10-meter walk test, or Medical Research Council sum scores of muscle power. However, for patients with LGMDR12 and intermediate-stage fatty replacement of muscle tissue (20%–70% proton density fat fraction), there was a significant worsening of Biodex Isometric Dynamometry even after 1 year. The investigators conclude this quantitative tool may be useful in monitoring clinical progression and response to targeted treatments for LGMDR12. Dr. Kawada expresses a concern regarding lead-time bias in the cohort (unclear time of disease onset in a recessive condition) which may have confounded any differences in the various qualitative and quantitative assessments over time. In response, the investigators confirmed that patients were included at the time of clinical symptom onset. Both investigators agree that sex-related differences in disease progression are less well understood, and additional studies are suggested to explore reasons for the variability in prognosis between sexes and age groups. De Wel et al. prospectively studied 24 patients with autosomal recessive limb-girdle muscular dystrophy type 12 (LGMDR12). Patients with LGMDR12 had no appreciable clinical worsening over a 2-year period according to repeated standardized clinical assessments, such as the 6-minute walk distance, 10-meter walk test, or Medical Research Council sum scores of muscle power. However, for patients with LGMDR12 and intermediate-stage fatty replacement of muscle tissue (20%–70% proton density fat fraction), there was a significant worsening of Biodex Isometric Dynamometry even after 1 year. The investigators conclude this quantitative tool may be useful in monitoring clinical progression and response to targeted treatments for LGMDR12. Dr. Kawada expresses a concern regarding lead-time bias in the cohort (unclear time of disease onset in a recessive condition) which may have confounded any differences in the various qualitative and quantitative assessments over time. In response, the investigators confirmed that patients were included at the time of clinical symptom onset. Both investigators agree that sex-related differences in disease progression are less well understood, and additional studies are suggested to explore reasons for the variability in prognosis between sexes and age groups.

The clinical, myopathological, and molecular characteristics of 26 Chinese patients with dysferlinopathy: a high proportion of misdiagnosis and novel variants

BackgroundDysferlinopathy is an autosomal recessive muscular dystrophy caused by pathogenic variants in the dysferlin (DYSF) gene. This disease shows heterogeneous clinical phenotypes and genetic characteristics.MethodsWe reviewed the clinical and pathological data as well as the molecular characteristics of 26 Chinese patients with dysferlinopathy screened by immunohistochemistry staining and pathogenic variants in DYSF genes.ResultsAmong 26 patients with dysferlinopathy, 18 patients (69.2%) presented as Limb-girdle Muscular Dystrophy Type R2 (LGMD R2), 4 (15.4%) had a phenotype of Miyoshi myopathy (MM), and 4 (15.4%) presented as asymptomatic hyperCKemia. Fifteen patients (57.7%) were originally misdiagnosed as inflammatory myopathy or other diseases. Fifteen novel variants were identified among the 40 variant sites identified in this cohort.ConclusionDysferlinopathy is a clinically and genetically heterogeneous group of disorders with various phenotypes, a high proportion of novel variants, and a high rate of misdiagnosis before immunohistochemistry staining and genetic analysis.

O.11 Identification of a novel heterozygous DYSF variant in a large family with a dominantly-inherited dysferlinopathy

Dysferlinopathy is an autosomal recessive muscular dystrophy, caused by bi-allelic variants in the gene encoding dysferlin (<i>DYSF</i>). Onset typically occurs in the second to third decade and is characterised by slowly progressive skeletal muscle weakness and atrophy of proximal and/or distal muscles of the limb girdles. There are rare cases of symptomatic <i>DYSF</i> variant carriers. Here, we report a large family with a dominantly inherited hyperCKemia and late-onset muscular dystrophy. Genetic analysis identified a co-segregating novel <i>DYSF</i> variant [NM_003494.4: c.6207del, p.(Tyr2070Metfs*4)]. No secondary variants in <i>DYSF</i> or other dystrophy-related genes were identified on whole genome sequencing and analysis of the proband's DNA. Skeletal muscle involvement was milder and later onset than typical dysferlinopathy presentations; these clinical signs manifested in only three individuals, all between the fourth and sixth decades of life. All individuals heterozygous for the c.6207del variant had hyperCKemia. Histological analysis of skeletal muscle biopsies across three generations showed clear dystrophic signs, including inflammatory infiltrate, regenerating myofibres, increased variability in myofibre size, and internal nuclei. Muscle magnetic resonance imaging revealed fatty replacement of muscle in two individuals. Western blot and immunohistochemical analysis of muscle biopsy demonstrated consistent reduction of dysferlin staining. Allele-specific quantitative PCR analysis of <i>DYSF</i> mRNA from patient muscle found that the variant, localised to the extreme C-terminus of dysferlin, does not activate post-transcriptional mRNA decay. We propose that this inheritance pattern may be underappreciated and that other late-onset muscular dystrophy cases with mono-allelic <i>DYSF</i> variants, particularly C-terminal premature truncation variants, may represent dominant forms of disease.

VP.78 Clinical and genetic study of LAMA2-related muscular dystrophy patients with seizures

<i>LAMA2</i>-related muscular dystrophy (LAMA2-MD) is an autosomal recessive muscular dystrophy caused by pathogenic variants in <i>LAMA2</i> gene, including two subgroups: severe, early-onset <i>LAMA2</i>-related congenital muscular dystrophy (LAMA2-CMD) and mild, late-onset autosomal recessive limb-girdle muscular dystrophy-23 (LGMD R23). Seizures frequently occurred in LAMA2-MD, however, the relationship between seizures and genotype in LAMA2-MD is not fully known. The clinical information of seizures including seizure type, frequency, treament, EEG changes, brain MRI and genetic data of LAMA2-MD patients from Peking University First Hospital between January 2003 and March 2022 were collected and analyzed. Among 141 LAMA2-MD patients, seizures were observed in 10.5% (13/124) of LAMA2-CMD patients and 29.4% (5/17) of LGMD R23 patients, including 14 patients with epilepsy and 4 patients with febrile seizures. The median (range) age of first seizure episode was 5 (0.1-20) years in LAMA2-CMD and 14 (1-24) years in LGMD R23. Eight patients with epilepsy showed focal seizures. Abnormal results of electroencephalography were found in 8/10 patients, manifesting as temporal, occipital or temporo-occipital epileptiform abnormalities. Brain magnetic resonance imaging (MRI) was performed in 16 patients with seizures, showing occipital pachygyria in 4 patients, cerebellum and brain stem dysplasia in 2 patients. Brain MRI of 41 LAMA2-MD patients without seizures were reassessed, showing occipital lobe pachygyria in 6 patients. Therefore, there was no significant association between seizures and occipital pachygyria in our cohort (P=0.18). Nine patients received antiepileptic drugs, while patients with occipital lobe pachygyria showed poor seizure control. The pathogenic variants included splice mutation (n=8), nonsense mutation (n=6) and frameshift mutation(n=6) in LAMA2-CMD patients, while missense mutation (n=5), frameshift mutation(n=4) in LGMD R23 patients. Compared with LAMA2-CMD, seizures were more frequently occurred in LGMD R23 patients and mainly manifested as focal seizures. No correlation between genotype and seizures was observed. In this study, we found that seizures occurred in 10.5% of LAMA2-CMD and 29.4% of LGMD R23 patients, and described the features of seizures in LAMA2-MD patients.

Homozygous Inversion on Chromosome 13 Involving SGCG Detected by Short Read Whole Genome Sequencing in a Patient Suffering from Limb-Girdle Muscular Dystrophy.

New techniques in molecular genetic diagnostics now allow for accurate diagnosis in a large proportion of patients with muscular diseases. Nevertheless, many patients remain unsolved, although the clinical history and/or the muscle biopsy give a clear indication of the involved genes. In many cases, there is a strong suspicion that the cause must lie in unexplored gene areas, such as deep-intronic or other non-coding regions. In order to find these changes, next-generation sequencing (NGS) methods are constantly evolving, making it possible to sequence entire genomes to reveal these previously uninvestigated regions. Here, we present a young woman who was strongly suspected of having a so far genetically unsolved sarcoglycanopathy based on her clinical history and muscle biopsy. Using short read whole genome sequencing (WGS), a homozygous inversion on chromosome 13 involving SGCG and LINC00621 was detected. The breakpoint in intron 2 of SGCG led to the absence of γ-sarcoglycan, resulting in the manifestation of autosomal recessive limb-girdle muscular dystrophy 5 (LGMDR5) in the young woman.

Identification of a novel heterozygous DYSF variant in a large family with a dominantly-inherited dysferlinopathy.

Dysferlinopathy is an autosomal recessive muscular dystrophy, caused by bi-allelic variants in the gene encoding dysferlin (DYSF). Onset typically occurs in the second to third decade and is characterised by slowly progressive skeletal muscle weakness and atrophy of the proximal and/or distal muscles of the four limbs. There are rare cases of symptomatic DYSF variant carriers. Here, we report a large family with a dominantly inherited hyperCKaemia and late-onset muscular dystrophy. Genetic analysis identified a co-segregating novel DYSF variant [NM_003494.4:c.6207del p.(Tyr2070Metfs*4)]. No secondary variants in DYSF or other dystrophy-related genes were identified on whole genome sequencing and analysis of the proband's DNA. Skeletal muscle involvement was milder and later onset than typical dysferlinopathy presentations; these clinical signs manifested in four individuals, all between the fourth and sixth decades of life. All individuals heterozygous for the c.6207del variant had hyperCKaemia. Histological analysis of skeletal muscle biopsies across three generations showed clear dystrophic signs, including inflammatory infiltrates, regenerating myofibres, increased variability in myofibre size and internal nuclei. Muscle magnetic resonance imaging revealed fatty replacement of muscle in two individuals. Western blot and immunohistochemical analysis of muscle biopsy demonstrated consistent reduction of dysferlin staining. Allele-specific quantitative PCR analysis of DYSF mRNA from patient muscle found that the variant, localised to the extreme C-terminus of dysferlin, does not activate post-transcriptional mRNA decay. We propose that this inheritance pattern may be underappreciated and that other late-onset muscular dystrophy cases with mono-allelic DYSF variants, particularly C-terminal premature truncation variants, may represent dominant forms of disease.

Molecular landscape of DYSF mutations in dysferlinopathy: From a Chinese multicenter analysis to a worldwide perspective.

Dysferlinopathy is one of the most common subgroup of autosomal recessive limb-girdle muscular dystrophies that is caused by mutations in DYSF gene. However, there is currently no worldwide comprehensive genetic analysis of DYSF variants. Through a national multicenter collaborative effort in China, we identified 222 DYSF variants with 40 novel variants from 245 patients. We then integrated DYSF variants from disease-related genetic databases including LOVD (n = 1020) and Clinvar (n = 1179), to depict the global landscape of disease-related DYSF variants. Normal-population-derived DSYF variants from gnomAD (n = 4318) and ChinaMAP (n = 13,330) were also analyzed in comparison. In Chinese patients, gender instead of genotype showed influence on the onset age of dysferlinopathy, with males showing an earlier age of onset. After integrative analysis, we identified two hotspot DYSF mutations, c.2997G>T in world patients and c.1375dup in Chinese patients, respectively. Both the pathogenic and likely pathogenic variants scattered on the whole gene length of DYSF. However, three specific domains (C2F-C2G-TM, DysF, and C2B-Ferl-C2C) contained variants at higher frequencies than reported in both the databases and Chinese patients. This study comprehensively collected available DYSF variant data, which may pave way for genetic counselling and future clinical trial design for gene therapies in dysferlinopathy.

Аutosomal recessive limb-girdle muscular dystrophy type 2A: two cases in Ukraine with different age of onset

The paper reports on two cases of young women from Ukraine with autosomal recessive limb-girdle muscular dystrophy type 2A with different age of symptoms onset and an absence of any family history presented with gradual onset of proximal muscle weakness in four limbs and thinning of shoulders, arms and thighs. Both patients had elevated creatine phosphokinase level and c.550delA mutations in CAPN3 gene. Sequence analysis and deletion/duplication testing of the 159 genes from skeletal muscles disease testing panel of 5-year-old girl identified deletion of exon 8 (heterozygous) and c.550delA (p.Thr184Argfs*36) mutation (heterozygous), were in CAPN3 gene. Magnetic Resonance Imaging of soft tissue of the proximal lower extremities was performed which showed signs of symmetrical atrophic changes in the major adductor muscle, the long and short adductor muscles, the semitendinosus muscle of the thigh, as a manifestations of autosomal recessive limb-girdle muscular dystrophy type 2A. Homozygous, pathogenic variant of the defect in the CAPN3 gene c.550del (p.Thr184Argfs * 36) was identified in a 25-year-old woman. Type 2A is the most common form of limb-girdle muscular dystrophy, accounting for about 30% of cases. The autosomal recessive limb-girdle muscular dystrophy type 2A is on caused by mutations in the CAPN3 gene, and it is characterized by selective atrophy and weakness of proximal limb and girdle muscles. The age of onset of muscle weakness is extremely variable; the most common being between 8 and 15 years, although it can range between 2 and 50 years. The diagnosis can be suspected by findings on a muscle biopsy or when a doctor experienced in muscular dystrophy examines you. A serum creatine kinase blood test may also show raised levels which indicate a problem in the muscles. The diagnosis has to be confirmed by means of identifying a mutation in the CAPN3 gene which is done on a deoxyribonucleic acid sample from a blood test. To date there are no specific treatments for limb-girdle muscular dystrophy, however careful management of the symptoms of the condition can improve a person’s quality of life. Joint contractures (tightening) can occur in limb-girdle muscular dystrophy and therefore regular physiotherapy is recommended.

LGMD: EP.177 Clinical and genetic spectrum of a large cohort of delta-sarcoglycan muscular dystrophy.

Sarcoglycanopathies comprise four subtypes of autosomal recessive limb-girdle muscular dystrophies (LGMDR3-6) that are caused by mutations in the SGCA, SGCB, SGCG and SGCD genes. Delta-sarcoglycanopathy (LGMDR6) is the least frequent of all sarcoglycanopaphies and it is considered an ultra-rare disease. Our aim was to characterize the clinical and genetic data of a large cohort of LGMDR6 patients and to investigate whether genetic or protein expression data could predict the severity of the disease. We contacted a total of 90 different neuromuscular units/neurology departments over the world and collected demographic, genetic, clinical and remaining protein expression in muscle biopsy data of patients with a genetic confirmed diagnosis of LGMDR6. We contacted more than 90 pediatric and adult neuromuscular units/neurology departments around the world and identified 23 patients from 9 different countries after reviewing genetic data of more than 10.000 patients with a neuromuscular disorder. There was a history of consanguinity in 87% of the patients and 52.2% of patients had another affected relative. Ninety-one percent of the patients were symptomatic at the time of the analysis. Upper and lower limb proximal muscle weakness was the most common presenting symptom. Distal muscle weakness was observed early on the progression of the disease. Cardiac involvement was observed in 5 patients (21.7%) and 4 patients (17.4%) required non-invasive ventilation. Sixty percent of patients were wheelchair-bound since a mean age of 14.6 years old. Patients with an undetectable expression of the sarcoglycan complex measure by muscle immunohistochemistry have a significant early onset of the disease and early age of lost ambulation compared to patients with residual protein expression. This study confirms that delta-sarcoglycanopathy is an ultra-rare neuromuscular condition and describes the clinical and molecular data of the largest cohort of patients reported so far. International collaboration has been crucial to collect these data. Our results show that this is a very severe and quickly progressive disease characterized by global muscle weakness affecting proximal and distal muscles of the limbs. As happen with other types of sarcoglycanopathy, there is a correlation between remaining protein expression, age at onset and disease's severity.