Limb girdle muscular dystrophy (LGMD) constitutes a group of genetically determined, progressive muscle weakness disorders, in which the pelvic or shoulder girdle musculature is predominantly or primarily involved. The prevalence of autosomal recessive and sporadic LGMD cases has been estimated to 5.7x10-6. LGMD2B is characterized by little shoulder girdle involvement and calf involvement. Age at onset is between the early teenage years and the late 30s. There is no clear evidence for cardiac involvement. Serum CK activity is always elevated. LGMD 2B is transmitted as an autosomal recessive form and is caused by mutation in the gene encoding dysferlin that is located on chromosome 2p12. Among cases of autosomal recessive LGMD, it has been estimated that 33% are caused by mutations in dysferlin. Dysferlin is a component of an active membrane repair process in skeletal muscle, and disruption of this process may produce the signs of muscular dystrophy. Miyoshi myopathy has been linked to the same locus on chromosome 2p and it is established that both LGMD2B and Miyoshi myopathy are different phenotypes of the same genotype. Both phenotypes can be encountered in the same sibship. Different subtypes of LGMD can now be distinguished by means of protein- and genetic analysis. No specific treatment is known and many patients receive physical therapy to prevent worsening of contractures.
Last update: October 2004