An X-linked recessive cardiomyopathy with abnormal mitochondria.

A transvascular endomyocardial biopsy from an infant with cardiomyopathy and chronic congestive heart failure showed abnormal mitochondria when examined by electron microscopy. At necropsy, similar abnormal mitochondria were seen in skeletal muscles, liver, and kidney. The patient's family pedigree revealed several male babies who had cardiac disease and died in infancy. Myocardium obtained at necropsy from three cousins contained mitochondria with abnormalities similar to those from the proband. An X-linked recessive cardiomyopathy seems likely in this family.