Maternally inherited mitochondrial cardiomyopathy associated with a C-to-T transition at nucleotide 3303 of mitochondrial DNA in the tRNA(Leu(UUR)) gene.

Disorders associated with mitochondrial DNA (mtDNA) mutations are usually dominated by involvement of the nervous system and skeletal muscle (hence the term "mitochondrial encephalomyopathies"). However, considering the high dependence of the heart on oxidative metabolism, it is not surprising that myocardial dysfunction is often a prominent feature in these disorders, either as isolated cardiomyopathy or as part of a multisystem mitochondrial syndrome. We report an infant with a maternally inherited C-to-T transition at nucleotide 3303 of mtDNA in the tRNA(Leu(UUR)) gene; this is the second kindred with cardiomyopathy identified to have this mutation of mitochondrial DNA. A brief review of other mitochondrial DNA defects is also included.