Fatal dilated cardiomyopathy associated with a mitochondrial DNA deletion

A 27-year-old man was admitted to hospital because of severe cardiac failur e. Investigation revealed dilated cardiomyopathy with a left ventricular ej ection fraction of 15-20%. During adolescence the patient had been investig ated for growth retardation and he also had progressive external ophthalmop legia. There had been no symptoms of cardiac disease until 2 weeks before a dmittance. An endomyocardial biopsy showed cardiomyocytes deficient in cyto chrome c oxidase (COX) in a mosaic pattern. A skeletal muscle biopsy showed mitochondrial myopathy with COX-deficient ragged-red fibers. Molecular gen etic analysis revealed a heteroplasmic, 3.8-kb, mitochondrial DNA (mtDNA) d eletion in heart and muscle. PCR-based quantification of the proportion of mtDNA with deletion showed 47% mutated mtDNA in the myocardial biopsy and 6 8% in muscle. In spite of treatment, the condition deteriorated and the pat ient died 5 days after admittance. This case demonstrates that mtDNA deleti ons may occasionally be the cause of severe dilated cardiomyopathy, and tha t morphological and molecular genetic diagnosis may be obtained by endomyoc ardial biopsy. Copyright (C) 2000 S. Karger AG, Basel.