Heart involvement in muscular dystrophies due to sarcoglycan gene mutations

Mutations in the sarcoglycan genes cause autosomal-recessive muscular dystr ophies. Because sarcoglycan genes and their protein products are highly exp ressed both in skeletal and cardiac muscle, patients with these mutations m ight be expected to be at risk to develop dilated cardiomyopathy. We theref ore studied 13 patients with alpha-, beta-, gamma-sarcoglycan gene mutation s by thorough cardiological assessment. Electrocardiographic or echocardiog raphic abnormalities were observed in about 30% of cases showing a severe c ourse of muscular dystrophy. No correlation was found between the presence of cardiac abnormalities and the type of mutation or sarcoglycan gene invol ved. The cardiac involvement was never severe, but it may be detected in ea rly stages of the muscle disease. The absence of overt cardiac dysfunction may be due to lower sarcoglycan protein expression in cardiac than skeletal muscle or to less sarcolemmal instability at the myocardial level, possibl y related to the different distribution of forces generated by contraction of the myocardium with respect to proximal limb-girdle muscles. (C) 1999 Jo hn Wiley & Sons, Inc.