Dieter Gläser

Muscle MRI findings in limb girdle muscular dystrophy type 2L

Limb girdle muscular dystrophy type 2L (LGMD2L) is an adult-onset slowly progressive muscular dystrophy associated with recessive mutations in the ANO5 gene. We analysed the muscle MRI pattern in a cohort of 25 LGMD2L patients in order to understand the extent and progression of muscle pathology in LGM2L and assess if muscle MRI might help in the diagnostic work-up of these patients. Our results showed a homogeneous pattern of muscle pathology on muscle MRI, with a predominant involvement of the posterior compartment muscles in both the thighs and calves. The muscles of the anterior compartments in the leg together with the sartorius and gracilis muscles were best preserved, which partially overlaps with patterns observed for other recessive LGMDs. Muscle MRI therefore does not appear to be as useful in the diagnostic work up of LGMD2L as for other neuromuscular diseases, such as Bethlem myopathy or myofibrillar myopathy.

ANO5 gene analysis in a large cohort of patients with anoctaminopathy: confirmation of male prevalence and high occurrence of the common exon 5 gene mutation

Limb girdle muscular dystrophy type 2L or anoctaminopathy is a condition mainly characterized by adult onset proximal lower limb muscular weakness and raised CK values, due to recessive ANO5 gene mutations. An exon 5 founder mutation (c.191dupA) has been identified in most of the British and German LGMD2L patients so far reported. We aimed to further investigate the prevalence and spectrum of ANO5 gene mutations and related clinical phenotypes, by screening 205 undiagnosed patients referred to our molecular service with a clinical suspicion of anoctaminopathy. A total of 42 unrelated patients had two ANO5 mutations (21%), whereas 14 carried a single change. We identified 34 pathogenic changes, 15 of which are novel. The c.191dupA mutation represents 61% of mutated alleles and appears to be less prevalent in non‐Northern European populations. Retrospective clinical analysis corroborates the prevalently proximal lower limb phenotype, the male predominance and absence of major cardiac or respiratory involvement. Identification of cases with isolated hyperCKaemia and very late symptomatic male and female subjects confirms the extension of the phenotypic spectrum of the disease. Anoctaminopathy appears to be one of the most common adult muscular dystrophies in Northern Europe, with a prevalence of about 20%–25% in unselected undiagnosed cases.

Analysis of spectrum and frequencies of mutations in McArdle disease. Identification of 13 novel mutations.

BackgroundMcArdle disease, a common metabolic myopathy with autosomal recessive inheritance, is caused by a frequent R50X mutation and many rare mutations in the myophosphorylase gene.ObjectivesTo identify spectrum and frequencies of myophosphorylase gene mutations in a large cohort of patients with McArdle disease, to discuss diagnostic implications, and to analyse genotype–phenotype relationship.MethodsMolecular genetic analysis of 56 index patients with muscle biopsy-proven myophosphorylase deficiency from Germany (n = 35), UK (n = 13), and several other countries (n = 8) was performed using direct sequencing.ResultsAllele frequency of the R50X mutation was 58%, and 71% of the patients carried this mutation at least on one allele. We detected 26 other less common mutations, 13 of which are novel: G157V, R161C, Q337R, E384K, S450L, G486D, R570W, K575E, IVS6-2A>T, IVS10+1G>A, R650X, c.1354insC, c.1155_1156delGG. There was no genotype-phenotype correlation with respect to age of onset and severity. R270X was the most frequent mutation among the less common mutations reaching an allele frequency of 5% followed by R94W and G686R representing a frequency of 4% each.ConclusionsThe study further extends the genetic heterogeneity of myophosphorylase gene mutations showing no mutational hotspot and no genotype–phenotype correlation. Most novel missense mutations were located in secondary structures or active sites of the enzyme. Some of the less common mutations are recurrent with different frequencies within Europe. Ethnic origin and frequency of less common mutations must be considered to establish efficient strategies in molecular genetic testing. Performing molecular testing can avoid muscle biopsy.

Homozygosity for the common GAA gene splice site mutation c.-32-13T>G in Pompe disease is associated with the classical adult phenotypical spectrum.

Homozygosity for the common Caucasian splice site mutation c.-32-13T>G in intron 1 of the GAA gene is rather rare in Pompe patients. We report on the clinical, biochemical, morphological, muscle imaging, and genetic findings of six adult Pompe patients from five unrelated families with the c.-32-13T>G GAA gene mutation in homozygous state. All patients had decreased GAA activity and elevated creatine kinase levels. Five patients, aged between 43 and 61 years (median 53 years), initially presented with myalgia, hyperCKaemia, and/or exercise induced fatigue at an age of onset (12-55 years). All but one had proximal lower limb weakness combined with axial weakness and moderate respiratory insufficiency; the sixth patient presented with hyperCKaemia only. Muscle biopsies showed PAS-positive vacuolar myopathy with lysosomal changes and reduced GAA activity. Muscle MRI of lower limb muscles revealed a moderate adipose substitution of the gluteal muscles, biceps femoris and slight fatty infiltration of all thigh muscles. One MRI of the respiratory muscles revealed a diaphragmatic atrophy with unilateral diaphragm elevation. So, the common Caucasian, so called mild, splice site mutation c.-32-13T>G in intron 1 of the GAA gene in a homozygote status reflects the full adult Pompe disease phenotype severity spectrum.

Clinicopathological analysis of the homozygous p.W1327X AGL mutation in glycogen storage disease type 3

We report on clinicopathological and whole body MRI analyses of the index patient of a large nonconsanguineous German‐Ukraine family with homozygous and heterozygous AGL gene mutations at position p.W1327X (c.3980G > A). There are only limited reports on this phenotype with a homozygous genotype. The index patient, a 49‐year‐old woman presented with hepatomegaly, cardiomyopathy and moderate progressive proximal limb myopathy. Skeletal muscle showed severe vacuolar myopathy with storage of PAS‐positive non‐membrane‐limited glycogen. An increase in glycogen content and completely decrease of debranching enzyme activity was measured in erythrocytes. Mutational analysis of the AGL gene showed a homozygous p.W1327X mutation. In the family, two brothers had been affected by severe infantile onset hepatomegaly and died within their first years of life by fatal liver cirrhosis. Furthermore, another sister severely affected by hepatomegaly, cardiomyopathy and proximal skeletal myopathy died at age 33. Three younger heterozygous sisters and a brother noticed exercise‐induced myalgia and weakness since their teens. In sum, a homozygous p.W1327X mutation leads to a severe generalized glycogenosis types 3a and 3b within the same family. Even heterozygous p.W1327X mutation carriers may present with mild non‐progressive neuromuscular symptoms, such as exercise‐induced myalgia and fatigue.

Two patients with GMPPB mutation: the overlapping phenotypes of limb-girdle myasthenic syndrome and limb-girdle muscular dystrophy dystroglycanopathy

Mutations in the guanosine diphosphate–mannose pyrophosphorylase‐B gene (GMPPB) have been identified in congenital muscular dystrophies, limb‐girdle muscular dystrophy (LGMD2T), and congenital myasthenic syndromes (CMSs); overall, 41 patients have been described.

Two patients with GMPPB mutation: the overlapping phenotypes of limb‐girdle myasthenic syndrome and LGMD2T dystroglycanopathy

Mutations in the guanosine diphosphate–mannose pyrophosphorylase‐B gene (GMPPB) have been identified in congenital muscular dystrophies, limb‐girdle muscular dystrophy (LGMD2T), and congenital myasthenic syndromes (CMSs); overall, 41 patients have been described.

Early infantile sensory-motor neuropathy with late onset respiratory distress.

Children with spinal muscular atrophy with respiratory distress (SMARD1) usually present within their first year of life, with respiratory failure due to diaphragmatic paralysis and progressive distal limb weakness. We present a child with a confirmed compound heterozygous IGHMBP2 mutation c.[676G>T];[2083A>T] in whom severe sensory-motor neuropathy preceded diaphragmatic paralysis by almost 3years. Autonomic system involvement with neurogenic bladder and urine retention were found at 3years. In summary, our patient highlights the broad spectrum of phenotypes observed in SMARD1. Currently, no prediction of phenotype according to genotype is possible, suggesting that yet unknown factors cause the observed phenotypic variation. Even in the absence of obvious diaphragmatic weakness, SMARD1 should be considered in severe infantile onset neuropathies. High throughput techniques, such as next generation sequencing, will possibly offer a useful approach in the heterogeneous group of inherited neuropathies.

Long-Term Observations in an Affected Family with Neurogenic Scapuloperoneal Syndrome Caused by Mutation R269C in the TRPV4 Gene.

Mutations in the TRPV4 gene, encoding a polymodal Ca(2+) permeable channel, are causative for several human diseases, affecting the skeletal and the peripheral nervous system with highly variable phenotypes. We report on a family with two affected individuals. The father clinically suffered from a classical scapuloperoneal syndrome, while the son presented with a severe neonatal onset with congenital respiratory distress, feeding problems and arthrogryposis multiplex. Multi-Gene Panel sequencing by next generation sequencing revealed the heterozygous mutation c.805C>T (p.R269C) in the TRPV4 gene. Long-term observation over two decades showed no relevant disease progression in the father and, after a dramatic neonatal period, a significant improvement in the son who became ambulant with orthoses at the age of 5 years, suggesting a reasonably good prognosis even in cases with severe neonatal onset. Long-term findings in muscle ultrasound correlated with the clinical course, showing stable or even slightly improved findings. Neurography revealed a late-onset sensory neuropathy in the father, which was so far not described in TRPV4 neuropathies.

Anoctamin 5 muscular dystrophy associated with a silent p.Leu115Leu mutation resulting in exon skipping.

We report a 45year-old patient with an asymmetrical proximal muscle weakness affecting the quadriceps muscle of the right leg starting at the age of 32years. CK was 25-fold increased. MRI of the legs showed signs of fatty degeneration more pronounced in the right side. Biopsy of a thigh muscle showed dystrophic pattern and amyloid deposition in blood vessel walls. The coding region and exon/intron boundaries of the ANO5 gene were amplified and sequenced. The common c.191dupA mutation and a silent novel p.Leu115Leu (c.345G>A) variant were identified. This silent variant was listed neither in the LOVD database nor in the SNP database. To evaluate the pathogenicity of the novel silent mutation in ANO5, cDNA analysis was performed that demonstrated skipping of exon 6. So far, no case with a silent mutation leading to abnormal splicing has been identified in Anoctamin 5 muscular dystrophy. Present findings emphasize that cDNA analysis should be done if a silent variant is not annotated in the databases. In Anoctamin 5 muscular dystrophy a molecular diagnosis is even more important as protein investigation through Western blotting or immunohistochemistry is not yet established.