Copy Number Variants Account for a Tiny Fraction of Undiagnosed Myopathic Patients.

Next-generation sequencing (NGS) technologies have led to an increase in the diagnosis of heterogeneous genetic conditions. However, over 50% of patients with a genetically inherited disease are still without a diagnosis. In these cases, different hypotheses are usually postulated, including variants in novel genes or elusive mutations.

Broad phenotypic spectrum and genotype-phenotype correlations in GMPPB-related dystroglycanopathies: an Italian cross-sectional study.

Background: Dystroglycanopathy (α-DG) is a relatively common, clinically and genetically heterogeneous category of congenital forms of muscular dystrophy (CMD) and limb-girdle muscular dystrophy (LGMD) associated with hypoglycosylated α-dystroglycan. To date, mutations in at least 19 genes have been associated with α-DG. One of them, GMPPB, encoding the guanosine-diphosphate-mannose (GDP-mannose) pyrophosphorylase B protein, has recently been associated with a wide clinical spectrum ranging from severe Walker-Warburg syndrome to pseudo-metabolic myopathy and even congenital myasthenic syndromes.

Autophagy dysregulation in Danon disease.

The autophagy-lysosome system is critical for muscle homeostasis and defects in lysosomal function result in a number of inherited muscle diseases, generally referred to as autophagic vacuolar myopathies (AVMs). Among them, Danon Disease (DD) and glycogen storage disease type II (GSDII) are due to primary lysosomal protein defects. DD is characterized by mutations in the lysosome-associated membrane protein 2 (LAMP2) gene.

Progress and challenges in diagnosis of dysferlinopathy.

Dysferlin-deficient limb girdle muscular dystrophy type 2B, distal Miyoshi myopathy, and other less frequent phenotypes are a group of recessive disorders called dysferlinopathies. They are characterized by wide clinical heterogeneity. To diagnose dysferlinopathy, a clinical neuromuscular workup, including electrophysiological and muscle imaging investigations, is essential to support subsequent laboratory testing.

Becker muscular dystrophy due to an intronic splicing mutation inducing a dual dystrophin transcript.

We describe a 29-year-old patient who complained of left thigh muscle weakness since he was 23 and of moderate proximal weakness of both lower limbs with difficulty in climbing stairs and running since he was 27. Mild weakness of iliopsoas and quadriceps muscles and muscle atrophy of both the distal forearm and thigh were observed upon clinical examination. He harboured a novel c.

Functional changes in Becker muscular dystrophy: implications for clinical trials in dystrophinopathies.

We performed a 1-year longitudinal study of Six Minute Walk Test (6MWT), North Star Ambulatory Assessment (NSAA), and timed function tests in Becker muscular dystrophy (BMD). Skeletal muscle dystrophin was quantified by immunoblot. We grouped deletions ending on exon 45 ("del 45-x", n = 28) or 51 ("del x-51", n = 10); isolated exon 48 deletion ("del 48", n = 10); and other mutations (n = 21).

The genetic basis of undiagnosed muscular dystrophies and myopathies: Results from 504 patients.

Objective: To apply next-generation sequencing (NGS) for the investigation of the genetic basis of undiagnosed muscular dystrophies and myopathies in a very large cohort of patients.

Methods: We applied an NGS-based platform named MotorPlex to our diagnostic workflow to test muscle disease genes with a high sensitivity and specificity for small DNA variants. We analyzed 504 undiagnosed patients mostly referred as being affected by limb-girdle muscular dystrophy or congenital myopathy.

Identification of an intragenic deletion in the SGCB gene through a re-evaluation of negative next generation sequencing results.

A large mutation screening of 504 patients with muscular dystrophy or myopathy has been performed by next generation sequencing (NGS). Among this cohort of patients, we report a case with a severe form of muscular dystrophy with a proximal weakness in the limb-girdle muscles. Her biopsy revealed typical dystrophic features and immunohistochemistry for α- and γ-sarcoglycans showed an absent reaction, addressing the clinical diagnosis toward a sarcoglycanopathy.

GYG1 gene mutations in a family with polyglucosan body myopathy.

Defects in enzymes involved in glycogen metabolism result in glycogen storage diseases (GSDs), which may affect the skeletal and sometimes also the cardiac muscle. The most frequent abnormality causing GSDs is glycogen storage, whereas other and uncommon forms of GSD are due to a perturbation of the branching structure of glycogen. These latter GSDs are characterized by an accumulation of polyglucosan (PG),(1) an abnormal polysaccharide with few branched points and excessively long peripheral chains.

Next generation sequencing detection of late onset pompe disease.

Introduction: We report a patient in whom the diagnosis of a treatable disease was delayed for 30 years.

Methods: Recent discoveries of next generation sequencing (NGS) have allowed us to reconsider the diagnosis of limb girdle muscular dystrophy (LGMD) cases of unknown etiology.

Results: A 36-year-old man appeared to have LGMD with onset in shoulder girdle muscles, but all sarcolemmal and cytoskeletal proteins tested by immunoblotting and immunohistochemistry gave normal results.

Protein and genetic diagnosis of limb girdle muscular dystrophy type 2A: The yield and the pitfalls.

Limb girdle muscular dystrophy type 2A (LGMD2A) is the most frequent form of LGMD worldwide. Comprehensive clinical assessment and laboratory testing is essential for diagnosis of LGMD2A. Muscle immunoblot analysis of calpain-3 is the most useful tool to direct genetic testing, as detection of calpain-3 deficiency has high diagnostic value.

Muscle fatigue, nNOS and muscle fiber atrophy in limb girdle muscular dystrophy.

Muscle fatigability and atrophy are frequent clinical signs in limb girdle muscular dystrophy (LGMD), but their pathogenetic mechanisms are still poorly understood. We review a series of different factors that may be connected in causing fatigue and atrophy, particularly considering the role of neuronal nitric oxide synthase (nNOS) and additional factors such as gender in different forms of LGMD (both recessive and dominant) underlying different pathogenetic mechanisms. In sarcoglycanopathies, the sarcolemmal nNOS reactivity varied from absent to reduced, depending on the residual level of sarcoglycan complex: in cases with complete sarcoglycan complex deficiency (mostly in beta-sarcoglycanopathy), the sarcolemmal nNOS reaction was absent and it was always associated with early severe clinical phenotype and cardiomyopathy.

Autophagy in Natural History and After ERT in Glycogenosis Type II.

We studied the role of autophagy in a series of 10 infantile-, juvenile-, and adult-onset GSDII patients and investigated autophagy blockade in successive biopsies of adult cases during disease natural history. We also correlated the autophagosome accumulation and efficiency of enzyme replacement therapy (ERT) in four treated cases (two infantile and two juvenile-adult onsets).The autophagic flux was monitored by measuring the amount of p62-positive protein aggregates and compared, together with fibre vacuolisation, to fibre atrophy.

Gender difference in limb-girdle muscular dystrophy: a muscle fiber morphometric study in 101 patients.

Aims: Limb girdle muscular dystrophies (LGMD), a genetically and clinically heterogeneous group of neuromuscular disorders, may show gender differences in the disease severity. We aimed to measure the extent of muscle fiber atrophy and evaluate possible gender differences at fiber level.

Methods: We conducted a thorough morphometric analysis of muscle fiber size and fiber area in 101 muscles from patients with various forms of LGMD (43 LGMD2A, 30 LGMD2B, 21 LGMD2C-2D-2E, 7 LGMD1C) and 12 normal controls.

Unveiling the degradative route of the V247M α-sarcoglycan mutant responsible for LGMD-2D.

Many membrane and secretory proteins that fail to pass quality control in the endoplasmic reticulum (ER) are dislocated into the cytosol and degraded by the proteasome. In applying rigid rules, however, quality control sometimes discharges proteins that, even though defective, retain their function. The unnecessary removal of such proteins represents the pathogenetic hallmark of diverse genetic diseases, in the case of ΔF508 mutant of cystic fibrosis transmembrane conductance regulator being probably the best known example.

Muscle atrophy, ubiquitin-proteasome, and autophagic pathways in dysferlinopathy.

Introduction: Muscle fiber atrophy and the molecular pathways underlying this process have not been investigated in dysferlinopathy patients.

Methods: In 22 muscles from dysferlinopathy patients we investigated fiber atrophy by morphometry and ubiquitin-proteasome and autophagic pathways using protein and/or transcriptional analysis of atrophy- and autophagy-related genes (MuRF1, atrogin1, LC3, p62, Bnip3).

Results: Dysferlinopathy showed significant fiber atrophy and higher MuRF-1 protein and mRNA levels, which correlated with fiber size, suggesting activation of the atrophy program by proteasome induction.

Next-generation sequencing identifies transportin 3 as the causative gene for LGMD1F.

Limb-girdle muscular dystrophies (LGMD) are genetically and clinically heterogeneous conditions. We investigated a large family with autosomal dominant transmission pattern, previously classified as LGMD1F and mapped to chromosome 7q32. Affected members are characterized by muscle weakness affecting earlier the pelvic girdle and the ileopsoas muscles.

Clinical phenotype, muscle MRI and muscle pathology of LGMD1F.

Of the seven autosomal dominant genetically distinct forms of LGMD so far described, in only four the causative gene has been identified (LGMD1A-1D). We describe clinical, histopathological and muscle MRI features of a large Italo-Spanish kindred with LGMD1F presenting proximal-limb and axial muscle weakness. We obtained complete clinical data and graded the progression of the disease in 29 patients.