Duchenne Muscular Dystrophy Carrier

Abstract

Heterozygous mutations in the DMD gene (Table 2.1) may be observed in female carriers of Duchenne muscular dystrophy. They are usually asymptomatic but may present with enlargement of calf muscles and muscle cramps. Some cases have overt muscle weakness or a severe myopathy, depending on the degree of random X-chromosome inactivation pattern. CK level is an important marker of carrier status, being elevated in about 70 % of carriers. The use of antibodies to dystrophin in muscle biopsy has improved the identification of carriers, showing single or clustered fibers with negative dystrophin labelling. DMD carriers are susceptible to develop a dilated cardiomyopathy, since cardiac muscle cells cannot regenerate and an unfavorable X-chromosome inactivation pattern may result in large groups of negative fibers. Conversely, the skeletal muscle is a syncytium where regeneration is possible, and some nuclei can migrate and compensate for the lack of dystrophin. In the DMD carrier here described, the most relevant sign was dilated cardiomyopathy that required cardiac transplantation.