MYOCARDIAL INVOLVEMENT IS VERY FREQUENT AMONG PATIENTS AFFECTED WITH SUBCLINICAL BECKERS MUSCULAR-DYSTROPHY

Background Several cases of Becker's muscular dystrophy (BMD) have bee n reported, which showed mild or subclinical skeletal muscle involveme nt with an overt dilated cardiomyopathy. Here, for the first time, a g roup of 28 patients with BMD who had a subclinical or benign myopathy have been studied through a thorough cardiological assessment. Methods and Results Each patient underwent ECG and echocardiographic examinat ions. Molecular analyses of the dystrophin gene and protein were perfo rmed. An unexpectedly high incidence of myocardial involvement was obs erved among patients affected with subclinical (72%) or benign (60%) B MD. The cardiac involvement appears to develop early from the right ve ntricle. Both the increase in left ventricular end-diastolic volume an d the reduction in the ejection fraction appeared to be age related. S evere left ventricular dilation with reduced ejection fraction, which could be complicated by life-threatening arrhythmias, may occur. Contr ary to previous reports, which indicated the involvement of 5'-end mut ations in cardiomyopathies as a result of dystrophin gene alterations, this study shows that despite the apparent concentration of deletions in two regions (5'-end and exons 47 through 49) no general conclusion s can be drawn regarding the involvement of specific gene mutations in the development of cardiomyopathy. Conclusions Cardiomyopathy is the main clinical feature and complication in patients affected by subclin ical or mild BMD. The cardiac manifestation is characterized by early right ventricular involvement and is later associated with left ventri cular impairment. In mild BMD, myocardial damage may develop because t he patients, who are unaware of a possible cardiac involvement, are st ill able to perform strenuous muscle exercise and, through pressure or volume overload, may induce mechanical stress, which is harmful for d ystrophin-deficient myocardial cells.