WHAT ACTUALLY CAUSES CARDIOMYOPATHY IN MD?
A The primary cause of cardiomyopathy in DMD and BMD is probably a lack of the protein dystrophin, the same protein deficiency that exists in the skeletal muscles and leads to generalized weakness, wasting and respiratory complications. Dystrophin is also needed by cardiac muscle, and its lack (complete in DMD and partial in BMD) probably leads to the loss of cardiac muscle cells under the stress of constant contraction. When heart problems do occur in other forms of MD, such as LGMD or congenital, it’s likely that the underlying cause is also a lack of a muscle protein. In four forms of LGMD, for example, the sarcoglycan proteins are known to lie near dystrophin in the muscle cell membrane, and their absence could be a factor in any heart problem in those disorders. But the story is a little more complicated. For instance, most people with DMD and BMD have heart involvement, but some don’t. And, in the sarcoglycan-deficient forms of LGMD, heart involvement is unusual, despite the prob
