Cardiac involvement in muscular dystrophies: molecular mechanisms.

In this review, we draw attention to the multiple mechanisms responsible for the pathogenesis of cardiomyopathies in patients with muscular dystrophies. More than one single mechanism is likely to be involved in the development of skeletal and cardiac muscle pathology even when there is a single protein defect. The best example is dystrophin deficiency, in which increased sarcolemmal permeability following eccentric exercise, reduced force generation, and abnormal signaling are all likely to contribute to the progressive muscle damage observed. In other conditions, such as the sarcoglycanopathies, a protein deficiency both in the striated cardiomyocte and the vascular smooth muscle appears to play a significant role. An entirely different mechanism of disease is likely in defects of nuclear envelope proteins, although the precise pathogenesis of this group of conditions is still not clear. Differences between the organization of skeletal and cardiac muscle protein complex are also only starting to emerge and will very likely be the focus of future research.