Disease with characteristics of variable degrees of muscle weakness due to progressive skeletal myopathy sometimes associated with dilated cardiomyopathy or left ventricle dilation. Duchenne and Becker muscular dystrophies primarily affect males and only a small percentage of female carriers have been reported to manifest these diseases. Symptomatic female carriers usually present later in life, muscle weakness is generally mild to moderate and is usually proximal and asymmetric, some patients present with cardiac manifestations alone. Females with clinical features are usually carriers of X-chromosome rearrangements, display skewed X-inactivation or have Turner syndrome. [from SNOMEDCT_US]