Cerebellar atrophy, Cerebral edema, Coma, Decreased activity of mitochondrial complex I, Decreased activity of mitochondrial respiratory chain, Decreased activity of the pyruvate dehydrogenase complex, Developmental regression, Diabetes mellitus, Dysarthria, Dyskinesia, Dystonia, Emotional lability, Encephalopathy, Exercise intolerance, Failure to thrive, Feeding difficulties, Feeding difficulties in infancy, Fetal distress, Focal T2 hyperintense basal ganglia lesion, Focal T2 hyperintense brainstem lesion, Generalized hypotonia, Global developmental delay, Growth delay, Hearing impairment, Hepatic failure, Hepatomegaly, Hyperreflexia, Hypertrichosis, Hypertrophic cardiomyopathy, Hypoglycemia, Hyporeflexia, Hypotonia, Increased CSF lactate, Increased circulating lactate concentration, Increased serum pyruvate, Intellectual disability, severe, Intrauterine growth retardation, Lactic acidosis, Lethargy, Leukodystrophy, Leukoencephalopathy, Metabolic acidosis, Microcephaly, Mitochondrial myopathy, Muscle weakness, Myoclonus, Nystagmus, Ophthalmoplegia, Optic atrophy, Optic disc pallor, Optic neuropathy, Paroxysmal involuntary eye movements, Peripheral neuropathy, Pigmentary retinopathy, Poor eye contact, Poor head control, Progressive cerebellar ataxia, Progressive macrocephaly, Progressive spastic paraplegia, Proximal tubulopathy, Ptosis, Respiratory insufficiency, Seizure, Sensorineural hearing impairment, Skeletal muscle atrophy, Spasticity, Strabismus, Ventricular septal defect, Vomiting