[Hypertrophic cardiomyopathy caused by cytochrome-oxidase deficiency]

Mitochondrial cytopathies are due to genetic anomalies in the oxidative phosphorylation enzymes (excepting Krebs cycle, pyruvate and certain other mitochondrial enzymes). Recently discovered, these diseases have a characteristic heterogeneous clinical expression because of the ubiquitous nature of this intracellular organelle. We observed a case in a 16-year-old girl who had cytochrome C oxidase deficiency. The child was born to non-consanguinous parents and had a healthy brother. The first manifestation of the disease was a systolic murmur heard at the age of 4 years. Progressively, exertion dyspnoea, lipothymia with cyanose led to the first echocardiography at 8 years revealing non-obstructive cardiomyopathy. Functional inadaptation of cardiac performance worsened requiring various symptomatic treatments. At the age of 16, the symptomatology included lower limb fatigue and the diagnosis of a metabolic disease was entertained. Phosphorylase A and B activity and phosphokinase activity were normal. High lactic acid levels after exertion suggested a mitochondrial enzyme deficiency. The diagnosis of cytochrome C oxidase deficiency was confirmed by spectrophotometric and polarographic assay of mitochondria from a peripheral muscle biopsy. Treatment with riboflavin, ascorbic acid, factor P, menadione, carnitine and iron sulfate has currently provided some symptomatic improvement. In patients with unexplained cardiomyopathy, the diagnosis of mitochondrial cytopathy should be entertained if oxidoreduction potentials (lactate/pyruvate ratio) are perturbed. The diagnosis is confirmed by enzyme studies of fresh muscle mitochondria. Currently therapeutic prospects are at best very poor. Genetic counselling may be advisable.