Fatal lactic acidosis due to deficiency of E1 component of the pyruvate dehydrogenase complex.

Pyruvate dehydrogenase complex deficiency is thought to be a common cause of lactic acidosis. We report a patient with lactic acidosis and intermittent weakness. The rate of oxidation of pyruvate by intact skeletal muscle and liver mitochondrial fractions was impaired and pyruvate dehydrogenase complex (PDC) activity was low. The amounts of immunoreactive dihydrolipoyl transacetylase and dihydrolipoyl dehydrogenase in liver and skeletal muscle mitochondrial fractions from the patient were normal. However, there were markedly lower concentrations of both the alpha and beta subunits of the E1 component of PDC.