| A rare neurometabolic disorder characterized typically by severe neonatal or early infantile encephalopathy, lactic acidosis and basal ganglia involvement. The majority of patients present with severe developmental delay, hypotonia, dystonia, seizures, failure to thrive, cardiomyopathy, liver steatosis and/or hepatomegaly and sensorineural hearing loss. Optic atrophy and nystagmus may also be present. A subset of patients (mostly with an onset in infancy) may present with a milder phenotype including paroxysmal dystonia, subtle gait abnormalities. In these patients, motor and cognitive development is near normal and usually no major cardiomyopathy, liver failure or severe lactic crises are present. |
