Development of cardiomyopathy in female carriers of Duchenne and Becker muscular dystrophies

Objective.-To characterize the presence and behavior of the dystrophinopathic myocardial damage in female carriers of a gene defect at the Xp21 locus of the X chromosome that causes Duchenne and Becker muscular dystrophies (DMD and BMD). Design.-Cohort study from April 1, 1985, to April 30, 1995, with cardiologic follow-up performed yearly for a minimum of 3 to a maximum of 10 years. Setting.-Counseling center for genetic muscular disorders, Patients.-A total of 197 women and girls aged 5 to 60 years ascertained to be carriers of the DMD (n=152) or BMD (n=45) gene. Main Outcome Measures.-Cardiac status at yearly examinations as determined by 12-lead electrocardiogram (ECG), 24-hour ambulatory ECG, M-mode and 2-dimensional echocardiography, and carotid pulse tracing. Myocardial scintigram was performed on each individual at least twice during the study, Immunohistochemical analysis of dystrophin from myocardium and/or skeletal muscle biopsy was performed in 12 carriers. Results.-Preclinical or clinically evident myocardial involvement was found in 166 cases (84.3%), without significant differences in percentage and behavior between DMD and BMD carriers. Its occurrence increased significantly with age, from 54.5% (18 cases) in carriers aged between 5 and 16 years to 90.2% (148 cases) in carriers older than 16 years. Dystrophin anomalies were detected at the membrane level of the myocardial fibers in all endomyocardial biopsy specimens. Conclusions.-Genetic anomalies can be considered the primary cause of myocardial damage in carriers of dystrophinopathic myopathies; myocardial damage shows the same behavior already described in DMD and BMD patients and progresses from preclinical to dilated cardiomyopathy, passing through stages of myocardial hypertrophy or dysrhythmias.