Leigh syndrome associated with a deficiency of the pyruvate dehydrogenase complex: results of treatment with a ketogenic diet.

A one-year-old boy suffering from intermittent lactic acidosis, muscular hypotonia, horizontal gaze paralysis and spasticity in both legs had low activity of the pyruvate dehydrogenase complex associated with low amounts of immunoreactive E 1 alpha and E 1 beta. Leigh syndrome was diagnosed on the basis of the clinical and biochemical abnormalities and the typical lesions observed on MRI of the brain. Treatment with a ketogenic diet was associated with clinical and biochemical amelioration. A striking improvement of the cerebral lesions was observed by neuro-imaging.