Collagen type VI myopathies.

Mutations in each of the three collagen VI genes COL6A1, COL6A2 and COL6A3 cause two main types of muscle disorders: Ullrich congenital muscular dystrophy, a severe phenotype, and a mild to moderate phenotype Bethlem myopathy. Recently, two additional phenotypes, including a limb-girdle muscular dystrophy phenotype and an autosomal recessive myosclerosis reported in one family with mutations in COL6A2 have been reported. Collagen VI is an important component of the extracellular matrix which forms a microfibrillar network that is found in close association with the cell and surrounding basement membrane.

The differential gene expression profiles of proximal and distal muscle groups are altered in pre-pathological dysferlin-deficient mice.

The selective pattern of muscle involvement is a key feature of muscular dystrophies. Dysferlinopathy is a good model for studying this process since it shows variable muscle involvement that can be highly selective even in individual patients. The transcriptomes of proximal and distal muscles from wildtype C57BL/10 and dysferlin deficient C57BL/10.

Subclinical semitendinosus and obturator externus involvement defines an autosomal dominant myopathy with early respiratory failure.

We recently described a dominant limb myopathy characterised by early respiratory failure whilst affected individuals were still ambulant (autosomal dominant myopathy with early respiratory failure). Early diagnosis and exclusion of this disorder is difficult because of the insidious onset in late adult life and the highly selective muscle involvement, both clinically and pathologically. We performed muscle magnetic resonance imaging on seven cases of autosomal dominant myopathy with early respiratory failure (age range 37-66 years, 4 male) and show selective early involvement of semitendinosus and obturator externus on magnetic resonance imaging that cannot be detected clinically, with different rates of progression in closely related muscles.