Brief report: deficiency of a dystrophin-associated glycoprotein (adhalin) in a patient with muscular dystrophy and cardiomyopathy.

C ARDIAC muscle is commonly affected in muscular dy~trophies.l-~ X-linked Duchenne's inuscular dystrophy and Becker's muscular dystrophy are caused by mutations in the gene encoding dystrophin,5,6 a membrane cytoskeletal p r ~ t e i n . ~ In skeletal and cardiac muscle, dystrophin is associated with a large oligomeric complex of sarcolemmal g lycopr~te ins .~~~ This dystrophin-glycoprotein complex is composed of five glycoproteins (35, 43 doublet, 50, and 156 kd) and two proteins (25 and 59 kd). It spans the sarcolemma to provide linkage between the subsarcolemmal cytoskeleton and laminin, a major component of the extracellular In Duchenne's and Becker's muscular dystrophies, the primary deficiency in dystrophin is associated with a commensurate secondary reduction in the other dystrophin-associated Disruption of the linkage between the cytoskeleton of the muscle fiber and the extracellular matrix has also been proposed as a factor in three autosomal recessive inherited diseases. In Fukuyama-type congenital muscular dystrophy, recently mapped to chromosome gq31-33,13 all the dystrophin-associated proteins, especially the 43-kd dystrophin-associated glycoprotein, have low expression.14 This disorder is associated with structural abnormalities in the brain.15 The second type is merosin-negative congenital muscular dystrophy, which has been linked to chromosome 6q2.16,17 Finally, severe childhood autosomal recessive muscular dystrophy has been attributed to a deficiency of the 50-kd dystrophin-associated glycoprotein.18 Severe childhood autosomal recessive muscular dystrophy is prevalent in North Africa, and its clinical presentation is similar to that of Duchenne's and Becker's muscular dystrophies except that both sexes are affected.lg The 50-kd dystrophin-associated glycoprotein was named "adhalin" from the Arabic adhal (muscle), and it has been linked in North African populations to an unidentified gene in the pericentromeric region of chromosome 13q.20 Adhalin deficiency has also been reported in Europe,21 Brazil," Japan,23 and P a k i ~ t a n . ~ ~ Interestingly,