Mitochondrial DNA transfer RNA mutation Leu(UUR)A-->G 3260: a second family with myopathy and cardiomyopathy.

A family with maternally inherited myopathy and cardiomyopathy is described. Mitochondrial DNA analysis showed a heteroplasmic point mutation at position 3260 in the leucine transfer RNA gene, previously reported in a large Italian family with a similar phenotype. This observation confirms pathogenicity of this mutation and suggests phenotypic specificity.