Recent advances in diagnosis of the childhood muscular dystrophies.

Recent advances in molecular genetics research have revolutionised our understanding of the childhood muscular dystrophies. The first breakthrough came in 1987 with the identification of the gene for dystrophin, the protein that is abnormal in X-linked Duchenne muscular dystrophy. Dystrophin is bound to a complex of proteins in the muscle membrane, and primary abnormalities of these proteins have now been identified as the cause of some autosomally inherited forms of muscular dystrophy. A group of transmembrane proteins known as alpha- (adhalin) beta-, gamma- and delta-sarcoglycan are deficient in autosomal recessive limb-girdle muscular dystrophy, and the extracellular matrix protein merosin (alpha2-laminin), is deficient in a subset of patients with congenital muscular dystrophy. Identification of primary deficiencies in these 'dystrophin associated proteins' will result in improved diagnostic accuracy, more accurate genetic counselling and, in some cases, the availability of prenatal diagnosis.