Cardiomyopathy is often found in patients with Duchenne and Becker mus
cular dystrophy, which are X Linked muscle diseases caused by mutation
s in the dystrophin gene. Dystrophin defects present in many different
ways and cases of mild Becker muscular dystrophy have been described
in which cardiomyopathy was severe. Female carriers of Duchenne muscul
ar dystrophy can develop symptomatic skeletal myopathy alone or combin
ed with dilated cardiomyopathy. They can also develop dilated cardiomy
opathy alone. X Linked dilated cardiomyopathy has been found in associ
ation with dystrophin defects. The relation between the molecular defe
cts and the cardiac phenotypes has not yet been established. New mutat
ions in the dystrophin gene are common and such mutations cause one th
ird of the cases with Duchenne and Becker muscular dystrophy. This mea
ns that sporadic cases of cardiomyopathy caused by dystrophin defects
are likely. This paper reports such a case in a boy of 14 who died of
dilated cardiomyopathy. Before the cardiac investigation, which was pe
rformed one month before he died, he had not complained of muscular we
akness. He had minor signs of limb girdle myopathy and slightly increa
sed concentrations of serum creatine kinase. He was found to have an u
nusual deletion in the dystrophin gene.