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Background: The Limb Girdle Muscular Dystrophies (LGMDs) are characterized by progressive weakness of the shoulder and hip girdle muscles as a result of over 30 different genetic mutations. This study is designed to develop clinical outcome assessments across the group of disorders. Methods/design: The primary goal of this study is to evaluate the utility of a set of outcome measures on a wide range of LGMD phenotypes and ability levels to determine if it would be possible to use similar outcomes between individuals with different phenotypes. We will perform a multi-center, 12-month study of 188 LGMD patients within the established Genetic Resolution and Assessments Solving Phenotypes in LGMD (GRASP-LGMD) Research Consortium, which is comprised of 11 sites in the United States and 2 sites in Europe. Enrolled patients will be clinically affected and have mutations in CAPN3 (LGMDR1), ANO5 (LGMDR12), DYSF (LGMDR2), DNAJB6 (LGMDD1), SGCA (LGMDR3), SGCB (LGMDR4), SGCD (LGMDR6), or SGCG (LGMDR5, or FKRP-related (LGMDR9). Discussion: To the best of our knowledge, this will be the largest consortium organized to prospectively validate clinical outcome assessments (COAs) in LGMD at its completion. These assessments will help clinical trial readiness by identifying reliable, valid, and responsive outcome measures as well as providing data driven clinical trial decision making for future clinical trials on therapeutic agents for LGMD. The results of this study will permit more efficient clinical trial design. All relevant data will be made available for investigators or companies involved in LGMD therapeutic development upon conclusion of this study as applicable. Trial registration: Clinicaltrials.gov NCT03981289; Date of registration: 6/10/2019. [ABSTRACT FROM AUTHOR]

Objective: Glycogen storage diseases (GSDs) are severe human disorders resulting from abnormal glucose metabolism, and all previously described GSDs segregate as autosomal recessive or X-linked traits. In this study, we aimed to molecularly characterize the first family with a dominant GSD.Methods: We describe a dominant GSD family with 13 affected members presenting with adult-onset muscle weakness, and we provide clinical, metabolic, histological, and ultrastructural data. We performed exome sequencing to uncover the causative gene, and functional experiments in the cell model and on recombinant proteins to investigate the pathogenic effect of the identified mutation.Results: We identified a heterozygous missense mutation in PYGM segregating with the disease in the family. PYGM codes for myophosphorylase, the enzyme catalyzing the initial step of glycogen breakdown. Enzymatic tests revealed that the PYGM mutation impairs the AMP-independent myophosphorylase activity, whereas the AMP-dependent activity was preserved. Further functional investigations demonstrated an altered conformation and aggregation of mutant myophosphorylase, and the concurrent accumulation of the intermediate filament desmin in the myofibers of the patients.Interpretation: Overall, this study describes the first example of a dominant glycogen storage disease in humans, and elucidates the underlying pathomechanisms by deciphering the sequence of events from the PYGM mutation to the accumulation of glycogen in the muscle fibers. ANN NEUROL 2020;88:274-282. [ABSTRACT FROM AUTHOR]

Introduction: Mutation in the collagen XII gene (COL12A1) was recently reported to induce Bethlem myopathy. We describe a family affected by collagen XII-related myopathy in 3 generations.Methods: Systematic interview, clinical examination, skin biopsies, and MRI of muscle were used.Results: The phenotype was characterized by neonatal hypotonia, contractures, and delayed motor development followed by resolution of contractures and a motor performance limited by reduced endurance. DNA analyses revealed a novel donor splice-site mutation in COL12A1 (c.8100 + 2T>C), which segregated with clinical affection and abnormal collagen XII retention in fibroblasts. MRI disclosed a selective wasting of the rectus femoris muscle.Discussion: COL12A1 mutations should be considered in patients with a mild Bethlem phenotype who present with selective wasting of the rectus femoris, absence of the outside-in phenomenon on MRI, and abnormal collagen XII retention in fibroblasts. Muscle Nerve 57: 1026-1030, 2018. [ABSTRACT FROM AUTHOR]

Key Clinical Message Studies have shown that difference in mt DNA mutation load among tissues is a result of postnatal modification. We present five family members with the m.8344A>G with variable phenotypes but uniform intrapersonal distribution of mutation load, indicating that there is no postnatal modification of mt DNA mutation load in this genotype. [ABSTRACT FROM AUTHOR]

The spinocerebellar ataxias (SCA) are a group of rare inherited neurodegenerative diseases characterized by slowly progressive cerebellar ataxia, resulting in unsteady gait, clumsiness, and dysarthria. The disorders are predominantly inherited in an autosomal dominant manner. Mutations in the gene AFG3L2 that encodes a subunit of the mitochondrial m-AAA protease have previously been shown to cause spinocerebellar ataxia type 28 (SCA28). Here, we present the clinical phenotypes of three patients from a family with autosomal dominant cerebellar ataxia and show by molecular genetics and in silico modelling that this is caused by a novel missense mutation in the AFG3L2 gene. Furthermore, we show, for the first time, fluorodeoxyglucose-positron emission tomography (FDG-PET) scans of the brain and selective type I fiber atrophy of skeletal muscle of SCA28 patients indicating non-nervous-system involvement in SCA28 as well. [ABSTRACT FROM AUTHOR]

Limb girdle muscular dystrophy type 2A is the most common limb girdle muscular dystrophy form worldwide. Although strict recessive inheritance is assumed, patients carrying a single mutation in the calpain 3 gene (CAPN3) are reported. Such findings are commonly attributed to incomplete mutation screening. In this investigation, we report 37 individuals (age range: 21-85 years, 21 females and 16 males) from 10 families in whom only one mutation in CAPN3 could be identified; a 21-bp, in-frame deletion (c.643_663del21). This mutation co-segregated with evidence of muscle disease and autosomal dominant transmission in several generations. Evidence of muscle disease was indicated by muscle pain, muscle weakness and wasting, significant fat replacement of muscles on imaging, myopathic changes on muscle biopsy and loss of calpain 3 protein on western blotting. Thirty-one of 34 patients had elevated creatine kinase or myoglobin. Muscle weakness was generally milder than observed in limb girdle muscular dystrophy type 2A, but affected the same muscle groups (proximal leg, lumbar paraspinal and medial gastrocnemius muscles). In some cases, the weakness was severely disabling. The 21-bp deletion did not affect mRNA maturation. Calpain 3 expression in muscle, assessed by western blot, was below 15% of normal levels in the nine mutation carriers in whom this could be tested. Haplotype analysis in four families from three different countries suggests that the 21-bp deletion is a founder mutation. This study provides strong evidence that heterozygosity for the c.643_663del21 deletion in CAPN3 results in a dominantly inherited muscle disease. The normal expression of mutated mRNA and the severe loss of calpain 3 on western blotting, suggest a dominant negative effect with a loss-of-function mechanism affecting the calpain 3 homodimer. This renders patients deficient in calpain 3 as in limb girdle muscular dystrophy type 2A, albeit in a milder form in most cases. Based on findings in 10 families, our study indicates that a dominantly inherited pattern of calpainopathy exists, and should be considered in the diagnostic work-up and genetic counselling of patients with calpainopathy and single-allele aberrations in CAPN3. [ABSTRACT FROM AUTHOR]

Introduction: Congenital myopathy due to mutations in the α-actin 1 gene (ACTA1) was identified in 1999, but knowledge of prevalence and phenotype in patients who survive 5 years is lacking.Methods: A national cohort of 91 patients aged ≥5 years and diagnosed with congenital myopathy was assessed for ACTA1 mutations and investigated clinically.Results: Four patients with ACTA1 mutations were identified, yielding a prevalence of 4.4%. Patients were 10-23 years of age, and all but 1 were ambulatory. Vital capacity ranged from 47% to 70% predicted, and 1 patient needed nocturnal bi-level positive airway pressure. Limb flexor/extensor muscles and upper and lower extremities were affected equally. Pronounced neck flexor weakness was noted.Conclusions: Congenital myopathy caused by ACTA1 mutations is fatal in infancy in most cases. This study shows that the prevalence of α-actin myopathy in older patients with congenital myopathy is not negligible and that phenotypes can be quite mild. [ABSTRACT FROM AUTHOR]

Congenital myopathies are a clinically and genetically heterogeneous group of muscle disorders characterized by congenital or early-onset hypotonia and muscle weakness, and specific pathological features on muscle biopsy. The phenotype ranges from foetal akinesia resulting in in utero or neonatal mortality, to milder disorders that are not life-limiting. Over the past decade, more than 20 new congenital myopathy genes have been identified. Most encode proteins involved in muscle contraction; however, mutations in ion channel-encoding genes are increasingly being recognized as a cause of this group of disorders. SCN4A encodes the α-subunit of the skeletal muscle voltage-gated sodium channel (Nav1.4). This channel is essential for the generation and propagation of the muscle action potential crucial to muscle contraction. Dominant SCN4A gain-of-function mutations are a well-established cause of myotonia and periodic paralysis. Using whole exome sequencing, we identified homozygous or compound heterozygous SCN4A mutations in a cohort of 11 individuals from six unrelated kindreds with congenital myopathy. Affected members developed in utero- or neonatal-onset muscle weakness of variable severity. In seven cases, severe muscle weakness resulted in death during the third trimester or shortly after birth. The remaining four cases had marked congenital or neonatal-onset hypotonia and weakness associated with mild-to-moderate facial and neck weakness, significant neonatal-onset respiratory and swallowing difficulties and childhood-onset spinal deformities. All four surviving cohort members experienced clinical improvement in the first decade of life. Muscle biopsies showed myopathic features including fibre size variability, presence of fibrofatty tissue of varying severity, without specific structural abnormalities. Electrophysiology suggested a myopathic process, without myotonia. In vitro functional assessment in HEK293 cells of the impact of the identified SCN4A mutations showed loss-of-function of the mutant Nav1.4 channels. All, apart from one, of the mutations either caused fully non-functional channels, or resulted in a reduced channel activity. Each of the affected cases carried at least one full loss-of-function mutation. In five out of six families, a second loss-of-function mutation was present on the trans allele. These functional results provide convincing evidence for the pathogenicity of the identified mutations and suggest that different degrees of loss-of-function in mutant Nav1.4 channels are associated with attenuation of the skeletal muscle action potential amplitude to a level insufficient to support normal muscle function. The results demonstrate that recessive loss-of-function SCN4A mutations should be considered in patients with a congenital myopathy. [ABSTRACT FROM AUTHOR]

We conducted a prospective multinational study of muscle pathology using magnetic resonance imaging (MRI) in patients with limb-girdle muscular dystrophy 2I (LGMD2I). Thirty eight adult ambulant LGMD2I patients (19 male; 19 female) with genetically identical mutations (c.826C>A) in the fukutin-related protein (FKRP) gene were recruited. In each patient, T1-weighted (T1w) imaging was assessed by qualitative grading for 15 individual lower limb muscles and quantitative Dixon imaging was analysed on 14 individual lower limb muscles by region of interest analysis. We described the pattern and appearance of muscle pathology and gender differences, not previously reported for LGMD2I. Diffuse fat infiltration of the gastrocnemii muscles was demonstrated in females, whereas in males fat infiltration was more prominent in the medial than the lateral gastrocnemius (p = 0.05). In the anterior thigh of males, in contrast to females, median fat infiltration in the vastus medialis muscle (45.7%) exceeded that in the vastus lateralis muscle (11.2%) (p<0.005). MRI is non-invasive, objective and does not rely on patient effort compared to clinical and physical measures that are currently employed. We demonstrated (i) that the quantitative Dixon technique is an objective quantitative marker of disease and (ii) new observations of gender specific patterns of muscle involvement in LGMD2I. [ABSTRACT FROM AUTHOR]

McArdle disease is an autosomal recessive disorder of muscle glycogen metabolism caused by pathogenic mutations in the PYGM gene, which encodes the skeletal muscle-specific isoform of glycogen phosphorylase. Clinical symptoms are mainly characterized by transient acute "crises" of early fatigue, myalgia and contractures, which can be accompanied by rhabdomyolysis. Owing to the difficulty of performing mechanistic studies in patients that often rely on invasive techniques, preclinical models have been used for decades, thereby contributing to gain insight into the pathophysiology and pathobiology of human diseases. In the present work, we describe the existing in vitro and in vivo preclinical models for McArdle disease and review the insights these models have provided. In addition, despite presenting some differences with the typical patient's phenotype, these models allow for a deep study of the different features of the disease while representing a necessary preclinical step to assess the efficacy and safety of possible treatments before they are tested in patients. [ABSTRACT FROM AUTHOR]

This study describes the clinical presentation and diagnosis in all Danish patients (49, 41 unrelated) with Wilson disease (WND). On the basis of the number of diagnosed patients from 1990-2008, the prevalence was estimated to be 1:49 500. Among routinely used diagnostic tests, none were consistently indicative of WND, with the exception of the 24-h urine-Cu test, which is always outside the normal range. Mutations were identified in 100% of the screened ATP7B alleles (70 unrelated), including five novel mutations: p.1021K; p.G1158V; p.L1304F; IVS20-2A>G; Ex5_6del. In all, 70% of mutations were found in exons 8, 14, 17, 18, and 20. The most frequent mutation, p.H1069Q, comprised 18%. We propose a new and simple model that correlates genotype and age of onset. By assuming that the milder of two mutations is 'functionally dominant' and determines the age of onset, we classified 25/27 mutations as either severe (age of onset <20 years) or moderate (age of onset >20 years), and correctly predicted the age of onset in 37/39 patients. This method should be tested in other Wilson populations. [ABSTRACT FROM AUTHOR]

Over 100 mutations in the myophosphorylase gene, which cause McArdle disease, are known. All these mutations have resulted in a complete block of muscle glycogenolysis, and accordingly, no genotype–phenotype correlation has been identified in this condition. We evaluated physiologic and genetic features of two patients with a variant form of McArdle disease, associated with unusually high exercise capacity. Physiologic findings were compared to those in 47 patients with typical McArdle disease, and 17 healthy subjects. Subjects performed an ischaemic forearm exercise test to assess lactate and ammonia production. Peak oxidative capacity (VO2max) and cardiac output were determined, using cycle ergometry as the exercise modality. The two patients with atypical McArdle disease carried common mutations on one allele (R50X and G205S), and novel splice mutations in introns 3 [IVS3-26A>G (c.425-26A>G)] and 5 [IVS5-601G>A (c.856-601G>A)] on the other allele. Plasma lactate after ischaemic exercise decreased in all typical McArdle patients, but increased in the two atypical McArdle patients (10% of that in healthy subjects). Peak workload and oxidative capacity were 2-fold higher in patients with atypical McArdle disease compared to typical McArdle patients. Oxygen uptake, relative to cardiac output, was severely impaired in the 47 patients with typical McArdle disease, and partially normalized in the milder affected McArdle patients. These findings identify the first distinct genotype-phenotype relationship in McArdle disease, and indicate that minimal myophosphorylase activity ameliorates the typical McArdle disease phenotype by augmenting muscle oxidative capacity. The milder form of McArdle disease provides important clues to the level of functional myophosphorylase needed to support muscle oxidative metabolism. [ABSTRACT FROM PUBLISHER]

Mutations in PYGM, encoding the muscle-specific glycogen phosphorylase (myophosphorylase), are responsible for McArdle disease. Among Caucasians, a large proportion of patients are homozygous for the R50X mutation, but other mutations can affect all the 20 exons of PYGM, making mutation detection laborious. We have developed a high-resolution melting (HRM) assay for mutation detection in PYGM. Twelve McArdle patients were investigated, in whom pre-screening had ruled out homozygosity or compound heterozygosity for the two common G205S and R50X mutations. In total, we identified 16 different variations. Thirteen of these are pathogenic, and three were classified as polymorphisms. Nine variations had not previously been described. One of the novel mutations, c.2430C > T, was initially predicted to result in a silent G810G change, but cDNA analysis demonstrated that the mutation led to abnormal mRNA processing. The HRM protocol reduced the need for direct sequencing by approximately 85%, and is a good approach to search for new mutations in PYGM. [ABSTRACT FROM AUTHOR]

Calpainopathy or limb-girdle muscular dystrophy type 2A (LGMD2A) is generally recognized as the most prevalent form of recessive LGMD and is caused by mutations in the CAPN3 gene. Out of a cohort of 119 patients fulfilling clinical criteria for LGMD2, referred to our neuromuscular clinic, 46 were suspected to have LGMD2A, based on western blot results. Four of these patients were shown to have LGMD2I upon molecular analysis, whereas 16 of the remaining 42 patients harbored mutations in CAPN3 by both direct genomic sequencing and cDNA analyses. In 10 patients, we identified both mutant alleles. In three other, only one heterozygous mutation could be identified on the genomic level; however, CAPN3 cDNA analyses demonstrated homozygosity for the mutant allele, indicating the presence of an unidentified allele that somehow compromise correct CAPN3 RNA processing. In the three remaining patients, only a single heterozygous mutation could be identified both at the genomic level and on full-length CAPN3 cDNA. All three patients exhibited a highly abnormal western blot for calpain-3 and clinical characteristics of LGMD2A. Only three of the genetically confirmed LGMD2A patients were of Danish origin, indicating a five- to sixfold lower prevalence in Denmark compared to other European countries. A total of 16 different CAPN3 mutations were identified, of which 5 were novel. The present study demonstrates the value of cDNA analysis for CAPN3 in LGMD2A patients and indicates that calpainopathy is an uncommon cause of LGMD in the Denmark.European Journal of Human Genetics (2008) 16, 935–940; doi:10.1038/ejhg.2008.47; published online 12 March 2008 [ABSTRACT FROM AUTHOR]

Using MRI, we evaluated the degree of involvement of muscles in the lower extremities of 18 unselected patients with facioscapulohumeral muscular dystrophy (FSHD). Findings were correlated with fragment size of the mutated gene, age, disease duration and muscle power. Most affected muscles were the hamstrings followed by the tibialis anterior and the medial gastrocnemius. The vastus-, gluteal- and peroneal muscles were the most unaffected, and the psoas muscle did not show evidence of involvement in any of the investigated subjects. Asymmetric involvement was evident in 15% of the investigated muscles on MRI and 6% on manual muscle strength testing. MRI findings in muscle tended to correlate with disease duration (r = 0.49; p < 0.05), but not with gene fragment size or age. MRI disclosed involvement of muscles performing hip flexion and ankle dorsal flexion that could not be detected by manual muscle strength testing. Otherwise, there was a close correlation (≈ r = 0.75; p < 0.0001) between muscle strength and MRI severity score for other muscle groups. The present study shows that MRI may disclose muscle involvement in FSHD that is not apparent on manual muscle testing, and suggests that MRI of muscle may be an important assessment tool in clinical trials involving patients with FSHD. [ABSTRACT FROM AUTHOR]

With the publication of a patient with severe exercise intolerance, in whom the mutated mtDNA in muscle was shown to be paternally inherited, the strict maternal inheritance of mtDNA was challenged. Paternal mtDNA inheritance may have gone unrecognized in cases of mitochondrial disease with no clear maternal pattern of inheritance because mitochondrial haplotypes are rarely investigated in diagnostic analyses. To find further evidence for a paternal inheritance of mtDNA, we reinvestigated 12 patients with mitochondrial myopathy, in whom the pathogenic mutation was known to be sporadic. We compared the mtDNA haplotypes from the patient''s muscle with that of the mtDNA haplotypes in blood from either the mother or the patient. No evidence of paternal inheritance of mtDNA was found in this small study. Although these findings indicate that the paternal inheritance of mtDNA is rare, they do not rule out that the phenomenon may occur at a rate that could still affect genetic counselling and anthropological research. [Copyright &y& Elsevier]

The article focuses on a study which investigates differences in molecular defects and morphology in levator palpebrae muscle (LPM) versus vastus lateralis muscle (VLM) in two patients, a 58-year old woman and 37-year old man with extraocular muscles (EOM) involvement and mitochondrial myopathy. It states that in both patients, proportion of COX-deficient and ragged blue fibers are higher in LPM. It mentions that the involvement of LPM was accompanied with higher mutation load.

Tubular aggregate myopathy is a genetically heterogeneous disease characterized by tubular aggregates as the hallmark on muscle biopsy. Mutations in STIM1 have recently been identified as one genetic cause in a number of tubular aggregate myopathy cases. To characterize the pattern of muscle involvement in this disease, upper and lower girdles and lower limbs were imaged in five patients with mutations in STIM1 , and the scans were compared with two patients with tubular aggregate myopathy not caused by mutations in STIM1 . A common pattern of involvement was found in STIM1 -mutated patients, although with variable extent and severity of lesions. In the upper girdle, the subscapularis muscle was invariably affected. In the lower limbs, all the patients showed a consistent involvement of the flexor hallucis longus, which is very rarely affected in other muscle diseases, and a diffuse involvement of thigh and posterior leg with sparing of gracilis, tibialis anterior and, to a lesser extent, short head of biceps femoris. Mutations in STIM1 are associated with a homogeneous involvement on imaging despite variable clinical features. Muscle imaging can be useful in identifying STIM1 -mutated patients especially among other forms of tubular aggregate myopathy. [ABSTRACT FROM AUTHOR]

Abstract: Congenital myopathies are difficult to classify correctly through molecular testing due to the size and heterogeneity of the genes involved. Therefore, the prevalence of the various genetic causes of congenital myopathies is largely unknown. In our cohort of 94 patients with congenital myopathy, two related female patients and two sporadic, male patients were found to carry mutations in the tropomyosin 2 (TPM2) and tropomyosin 3 (TPM3) genes, respectively. This indicates a low (4.3%) frequency of TPM2 and TPM3 mutations as a cause of congenital myopathy. Compared to previously described patients carrying the same mutations as found in our study (c.503G>A, and c.502C>T in TPM3, and c.415_417delGAG in TPM2), clinical presentation and muscle morphological findings differed in our patients. Differences included variation in distribution of muscle weakness, presence of scoliosis and ptosis, physical performance and joint contractures. The variation in clinical profiles emphasizes the phenotypic heterogeneity. However, common features were also present, such as onset of symptoms in infancy or childhood, musculoskeletal deformities and normal or low plasma levels of creatine kinase. One patient had nemaline myopathy and fiber size disproportion, while three patients had congenital fiber type disproportion (CFTD) on muscle biopsies. TPM2-related CFTD has only been described in two cases, indicating that mutations in TPM2 are rare causes of CFTD. [Copyright &y& Elsevier]

Abstract: Most patients with mutations in the tRNAlys gene (MTTK) present with symptoms from the central nervous system (CNS). We describe a 41-year-old woman with pure myopathy associated with a novel de novo mtDNA mutation, mt.8340G>A, which was heteroplasmic in muscle (53%), blood, urine and mouth epithelial cells (<7%). No other family members, including her mother, carried the mutation. She presented with exercise intolerance from age 9, and since age 20 she experienced ptosis and reduced ocular motility. A muscle biopsy revealed ragged red fibres (10%), no COX negative fibres, and many fibres with central nuclei (30%), indicating ongoing damage and repair. The present case expands the mutational and phenotypic spectrum of diseases associated with mutations in MTTK. [Copyright &y& Elsevier]