Collagenopathy (Ullrich congenital muscular dystrophy, Bethlem myopathy)]

Collagenopathies with collagen VI mutations include Ullrich congenital muscular dystrophy (Ullrich's disease) and Bethlem myopathy. Patients with Ullrich's disease have generalized muscle weakness, multiple contractures of the proximal joints and hyperextensibility of the distal joints. Bethlem myopathy is characterized by the combination of proximal muscle weakness and contractures of finger, elbow, and ankle joints. We found for the first time a deficiency of collagen VI in Ullrich's disease. Furthermore, we found an abnormality of cell adhesion and abnormal regeneration or maturation in Ullrich's disease. Mutations in the genes COL6A1, COL6A2, COL6A3 are associated with Ullrich's disease and Bethlem myopathy. Bethlem myopathy is inherited in an autosomal dominant manner and Ullrich's disease usually in an autosomal recessive manner. Recently, de novo dominant mutations are reported in Ullrich's disease. We evaluated the role of nonsense-mediated mRNA decay (NMD) in Ullrich's disease that has a frameshift mutation with a premature termination codon in the COL6A2 gene causing the loss of collagen VI. The pharmacological block of NMD caused upregulation of the mutant collagen VI and partially functional extracellular matrix formation. Our results suggest that NMD inhibitors can be used as a therapeutic tool to rescue some human genetic diseases exacerbated by NMD.     

Novel mutations in collagen VI genes: expansion of the Bethlem myopathy phenotype

OBJECTIVE: To investigate the molecular basis of autosomal dominant limb-girdle muscular dystrophy (AD-LGMD) in three large new families. METHODS AND RESULTS: Genome-wide linkage was performed to show that the causative gene in all three families localized to chromosome 21q22.3 (Zmax = 10.3; theta = 0). This region contained the collagen VI alpha1 and alpha2 genes, which have been previously shown to harbor mutations causing a relatively mild congenital myopathy with contractures (Bethlem myopathy). Screening of the collagen VI alpha1 and alpha2 genes revealed novel, causative mutations in each family (COL6A1-K121R, G341D; COL6A2-D620N); two of these mutations were in novel regions of the proteins not previously associated with disease. Collagen VI is a ubiquitously expressed component of connective tissue; however, both limb-girdle muscular dystrophy and Bethlem myopathy patients show symptoms restricted to skeletal muscle. To address the muscle-specific symptoms resulting from collagen VI mutations, the authors studied three patient muscle biopsies at the molecular level (protein expression). A marked reduction of laminin beta1 protein in the myofiber basal lamina in all biopsies was found, although this protein was expressed normally in the neighboring capillary basal laminae. CONCLUSIONS: The authors' studies widen the clinical spectrum of Bethlem myopathy and suggest collagen VI etiology should be investigated in dominant limb-girdle muscular dystrophy. The authors hypothesize that collagen VI mutations lead to muscle-specific defects of the basal lamina, and may explain the muscle-specific symptoms of Bethlem and limb-girdle muscular dystrophy patients with collagen VI mutations.     

Early-onset benign autosomal-dominant limb-girdle myopathy with contractures (Bethlem myopathy)

We report the first Japanese patients, a mother and son, with early-onset, benign, autosomal-dominant, limb-girdle myopathy with contractures (Bethlem myopathy). The clinical features revealed predominantly proximal muscle weakness--especially in the limb-girdle muscles--joint contractures increasing with age, a benign course, and the absence of cardiac involvement. Muscle histology revealed nonspecific myopathy changes without dystrophic features. Electromyogram revealed a reduced interference pattern with a giant spike suggesting a neurogenic process.     

Collagen VI-related muscle disorders

Collagen VI-related muscle disorders include severe Ullrich's disease (Ullrich congenital muscular dystrophy:UCMD) and milder Bethlem myopathy. Mutations in the 3 collagen VI genes, namely, COL6A1, COL6A2, and COL6A3, cause both diseases. UCMD is inherited in an autosomal recessive manner, and de novo dominant mutations are also reported. Bethlem myopathy is usually inherited in an autosomal dominant manner, but a rare autosomal recessive inheritance has recently been reported. Patients with UCMD have generalized muscle weakness, multiple contractures of the proximal joints, and hyperextensibility of the distal joints. Bethlem myopathy is characterized by a combination of proximal muscle weakness and contractures of finger, elbow, and ankle joints. Because intermediate phenotypes occur, UCMD and Bethlem myopathy should be considered diseases in a continuous spectrum of collagen VI-related muscle disorders. Abnormalities of cell adhesion, regeneration, mitochondrial permeability transition pore, and autophagy have been reported in UCMD. Respiratory surveillance for nocturnal hypoventilation and proper respirator implementation are crinical management considerations in UCMD. Orthopedic assessment in necessary if surgery for Achilles tendon contractures is being considered in patient with Bethlem myopathy. We evaluated the role of nonsense-mediated mRNA decay (NMD) in UCMD associated with a premature termination codon in the COL6A2 gene, which caused the loss of collagen VI. A pharmacological block of NMD caused upregulation of the mutant collagen VI and partially functional extracellular matrix formation. Cyclosporin A has been reported to correct mitochondrial dysfunction and muscle apoptosis in patients with collagen VI myopathies, and a pilot trial of cyclosporin A was carried out.     

Early-onset benign autosomal dominant limb-girdle myopathy with contractures (Bethlem myopathy)

We report a large French-Canadian kindred with 33 affected members in six generations showing early-onset autosomal dominant limb-girdle myopathy and contractures. This myopathy is unique because of its benign course, with many members only minimally impaired even in old age. Examination of affected members revealed mild to moderate proximal weakness and wasting. Contractures were observed at the elbows and ankles in all, while in some they were more widespread. Serum CK was either normal or slightly raised, and electrodiagnostic studies suggested a primary myopathy. Muscle biopsy revealed nonspecific features of a myopathy without fiber necrosis or regeneration. Cardiac involvement was absent clinically in all patients and at autopsy in two affected individuals. The similarities between four previously reported families and our own establishes this myopathy as a distinct clinicogenetic entity, for which we propose the name "Bethlem myopathy."     

Early-onset benign autosomal dominant limb-girdle myopathy with contractures (Bethlem myopathy) in a Japanese family]

We report a family showing an early-onset benign autosomal dominant limb-girdle myopathy with contractures. The clinical features in our family included; 1) slowly progressive limb-girdle muscle weakness since childhood. 2) contractures of fingers, elbows and ankles, 3) mild motor impairment with preserved activities of daily living. The disease was inherited through an autosomal dominant trait. Muscle pathology revealed variation in fiber size, slightly increased central nuclei, mild endomysial fibrosis, type 1 fiber predominance and type 2 fiber atrophy. The above clinical features were similar to those seen in patients reported by Bethlem (1976) and Mohire (1988), and therefore we made a diagnosis of Bethlem myopathy on this familial patients which was extremely rare in Japan.     

Autosomal recessive Bethlem myopathy: A clinical,genetic and functional study

Bethlem myopathy represents the milder form of the spectrum of Collagen VI-related dystrophies, which are characterized by a clinical continuum between the two extremities, the Bethlem myopathy and the Ullrich congenital muscular dystrophy, and include less defined intermediate phenotypes. Bethlem myopathy is mainly an autosomal dominant disorder and the causing mutations occur in the COL6A genes encoding for the α1 (COL6A1), α2 (COL6A2) and α3 (COL6A3) chains. However, few cases of recessive inheritance have been also reported. We here describe clinical, genetic and functional findings in a recessive Bethlem myopathy family harbouring two novel pathogenic mutations in the COL6A2 gene. Two adult siblings presented with muscle weakness and wasting, elbows and Achilles tendon retractions, lumbar hyperlordosis, waddling gait and positive Gowers' sign. Muscle biopsy showed a dystrophic pattern. Molecular analysis of the COL6A2 gene revealed the novel paternally-inherited nonsense p.Gln889* mutation and the maternally-inherited p.Pro260_Lys261insProPro small insertion. Fibroblast studies in both affected patients showed the concomitant reduction in the amount of normal Collagen VI (p.Gln889*) and impairment of Collagen VI secretion and assembly (p.Pro260_Lys261insProPro). Each of the two variants behave as a recessive mutation as shown by the asymptomatic heterozygous parents, while their concomitant effects determined a relatively mild Bethlem myopathy phenotype. This study confirms the occurrence of recessive inherited Bethlem myopathy and expands the genetic heterogeneity of this group of muscle diseases.     

Collagen XII myopathy with rectus femoris atrophy and collagen XII retention in fibroblasts

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     

Decreased expression of laminin beta 1 in chromosome 21-linked Bethlem myopathy.

Muscle biopsies of four patients affected by chromosome 21-linked Bethlem myopathy were investigated by means of immunohistochemistry, with monoclonal antibodies for laminin chains, dystrophin and dystrophin associated glycoproteins. The objective of this study was to determine whether an altered molecular structure of collagen type VI, characteristic of Bethlem myopathy, could influence the expression of the protein complex linking the extracellular matrix with the subsarcolemmal cytoskeleton. Normal expression of all proteins was found except for laminin beta 1, along with an age related progressive deficiency of this protein in the muscle fibre basal lamina. This study shows that Bethlem myopathy linked to chromosome 21 is associated with a secondary decrease in laminin beta 1 expression.     

Autosomal recessive inheritance of classic Bethlem myopathy

Mutations in the collagen VI genes (COL6A1, COL6A2 and COL6A3) result in Ullrich congenital muscular dystrophy (CMD), Bethlem myopathy or phenotypes intermediate between Ullrich CMD and Bethlem myopathy. While Ullrich CMD can be caused by either recessively or dominantly acting mutations, Bethlem myopathy has thus far been described as an exclusively autosomal dominant condition. We report two adult siblings with classic Bethlem myopathy who are compound heterozygous for a single nucleotide deletion (exon 23; c.1770delG), leading to in-frame skipping of exon 23 on the maternal allele, and a missense mutation p.R830W in exon 28 on the paternal allele. The parents are carriers of the respective mutations and are clinically unaffected. The exon skipping mutation in exon 23 results in a chain incapable of heterotrimeric assembly, while p.R830W likely ameliorates the phenotype into the Bethlem range. Thus, autosomal recessive inheritance can also underlie Bethlem myopathy, supporting the notion that Ullrich CMD and Bethlem myopathy are part of a common clinical and genetic spectrum.     

Bethlem myopathy: Early-onset benign autosomal dominant myopathy with contractures. Description of two new families

Bethlem myopathy is an apparently rare early-onset benign autosomal dominant limb-girdle myopathy with contractures of the fingers. To determine whether this disorder is unrecognized rather than rare we used muscle computerized tomography (CT) and isokinetic muscle testing and assiduously sought contractures of the fingers in relatives of two patients with the disease. CT showed that muscle impairment was mild but more diffuse than clinically apparent and showed an unexpected progressive degeneration of lumbar paravertebral muscles. The isokinetic test showed that the quadriceps was more involved than the hamstrings. In addition we found that contractures of the last four fingers progressed centripetally with age from the distal interphalangeal joints to the wrist. As a result we proved that 15 of the 21 examined subjects had the disease, 7 of them being unaware that anything was amiss. Careful examination may reveal that Bethlem myopathy is more common than is now thought.     

Electrocardiographic findings in mdx mice: a cardiac phenotype of Duchenne muscular dystrophy

Bethlem myopathy is an early-onset benign myopathy characterized by proximal muscular weakness and multiple flexion contractures. It is a dominantly inherited disorder associated with mutations in the three COL6 genes encoding type VI collagen. We detected a g-->a substitution at +1 position of COL6A1 intron 3 in a four-generation Italian family affected by a mild form of Bethlem myopathy. The mutation results in the activation of a cryptic splice donor site at the 3' end of exon 3, leading to the loss of 66 nucleotides and an "in-frame" deletion of 22 amino acids in the NH2-domain. Molecular analysis on fibroblasts of the propositus showed that the mutated mRNA was present and stable, but the mutated protein could not be detected. Western blot and immunofluorescence analyses showed a decreased level of collagen VI synthesis and deposition in fibroblasts of the propositus. Together, the results suggest that the mutated protein was highly unstable and rapidly degraded, and that the mild phenotype was caused by a reduced amount of normal collagen VI microfibrils. In addition, we demonstrated that lymphocytes can be used for the first mutation screening analysis of patients with Bethlem myopathy.     

Muscle MRI in Ullrich congenital muscular dystrophy and Bethlem myopathy

The aim of this study was to evaluate the spectrum of muscle involvement on Magnetic Resonance Imaging (MRI) in patients with collagen VI related disorders. Nineteen patients with genetically confirmed collagen VI related disorders, 10 with Bethlem myopathy and 9 with Ullrich congenital muscular dystrophy (CMD), had muscle MRI of their legs using T1 sequences through calves and thighs. In patients with Bethlem myopathy the vasti muscles appeared to be the most frequently and most strikingly affected thigh muscles, with a rim of abnormal signal at the periphery of each muscle and relative sparing of the central part. Another frequent finding was the presence of a peculiar involvement of the rectus femoris with a central area of abnormal signal within the muscle. Patients with Ullrich CMD had a more diffuse involvement of the thigh muscles with relative sparing of sartorius, gracilis and adductor longus. In 8 of the 9 patients with Ullrich CMD, we also observed the peripheral rim of the vastus lateralis and the central area in the rectus femoris observed in patients with Bethlem myopathy. At calf level the results were more variable but a significant proportion of patients with both Bethlem myopathy (8/10) and Ullrich CMD (6/9) showed a rim of abnormal signal at the periphery of soleus and gastrocnemii. Bethlem myopathy and Ullrich CMD patients have distinct patterns of muscle involvement on MRI with some overlap between the two forms. Our results suggest that muscle MR may be used, as an additional tool, to identify patients with collagen VI related disorders. This information is even more important in the patients with a typical Ullrich CMD clinical phenotype but with normal collagen expression of VI in muscle and/or skin.     

Bethlem肌病一家系临床表型及基因突变分析

目的 分析Bethlem肌病临床表型和基因突变特点.方法 报道一家系3例女性患者临床表型、肌电图、肌肉活检、肌肉病理学和基因检测结果,并结合相关文献进行分析.结果 先证者于13岁发病,以进行性四肢近端无力为主要临床表现.血清学肌酸激酶水平显著升高,肌电图呈肌源性损害,肌肉病理学显示骨骼肌局灶坏死等非特异性肌源性损害.基...     

Collagen VI‐related myopathy: Expanding the clinical and genetic spectrum

Introduction: We aimed to analyze the clinical and genetic characteristics of collagen VI‐related myopathy. Methods: We analyzed the clinical course and mutation spectrum in patients with collagen VI gene mutations among our congenital muscular dystrophy cohort. Results: Among 24 patients with mutations in collagen VI coding genes, 13 (54.2%) were categorized as Ullrich type, and 11 (45.8%) as non‐Ullrich type. Congenital orthopedic problems were similarly observed in both types, yet multiple joint contractures were found only in the Ullrich type. Clinical courses and pathology findings varied between patients. Mutations in COL6A1, COL6A2, and COL6A3 were found in 15 (65%), 3 (13%), and 5 (22%) patients, respectively, without genotype–phenotype association. Five novel variants were detected. Discussion: We verified clinical heterogeneity of collagen VI‐related myopathy, which emphasizes the importance of genetic testing. Genotype–phenotype association or early predictors for progression were not identified. Multiple joint contractures predict rapid deterioration. Muscle Nerve 58 : 381–388, 2018     

Differentiating Emery-Dreifuss muscular dystrophy and collagen VI-related myopathies using a specific CT scanner pattern

Bethlem myopathy and Ullrich congenital muscular dystrophy are part of the heterogeneous group of collagen VI-related muscle disorders. They are caused by mutations in collagen VI (ColVI) genes (COL6A1, COL6A2, and COL6A3) while LMNA mutations cause autosomal dominant Emery-Dreifuss muscular dystrophy. A muscular dystrophy pattern and contractures are found in all three conditions, making differential diagnosis difficult especially in young patients when cardiomyopathy is absent.We retrospectively assessed upper and lower limb muscle CT scans in 14 Bethlem/Ullrich patients and 13 Emery-Dreifuss patients with identified mutations.CT was able to differentiate Emery-Dreifuss muscular dystrophy from ColVI-related myopathies in selected thigh muscles and to a lesser extent calves muscles: rectus femoris fatty infiltration was selectively present in Bethlem/Ullrich patients while posterior thigh muscles infiltration was more prominently found in Emery-Dreifuss patients. A more severe fatty infiltration particularly in the leg posterior compartment was found in the Emery-Dreifuss group.     

Autosomal dominant myopathy with congenital joint contractures,ophthalmoplegia, and rimmed vacuoles

We describe a new myopathy in a large family with 19 affected cases. Inheritance was autosomal dominant. Characteristic clinical features were congenital joint contractures, which normalized during early childhood, external ophthalmoplegia, and proximal muscle weakness. Muscle atrophy was most prominent in the pectoralis and quadriceps muscles. The clinical course was nonprogressive in childhood, but most adult cases experienced deterioration of muscle function, starting from 30 to 50 years of age. The major histopathological change of skeletal muscle in childhood was focal disorganization of myofilaments. In adults with progressive muscle weakness, the muscle biopsies showed dystrophic changes and rimmed vacuoles with cytoplasmic and intranuclear inclusions of 15- to 21-nm filaments. These findings suggests that this new disease should be classified as a variant of hereditary inclusion body myopathy.     

Mitochondria-lipid-glycogen myopathy, hyperlactacidemia, and carnitine deficiency

A 25-month-old girl had proximal myopathy, increased blood lactate and pyruvate concentrations, and transient ketoacidosis. Muscle biopsy revealed vacuolar myopathy with accumulation of both lipid and glycogen. Electronmicroscopy also showed abnormalities in the shape, size, and internal structure of muscle mitochondria. Carnitine content of skeletal muscle was reduced. Short-chain and long-chain acyl-carnitines were augmented in both plasma and skeletal muscle. Oral carnitine therapy improved muscle strength.