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, Dysphagia, 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 circulating lactate concentration, Increased circulating pyruvate concentration, Increased CSF lactate, Intellectual disability, severe, Intrauterine growth retardation, Irritability, Lactic acidosis, Lethargy, Leukodystrophy, Leukoencephalopathy, Microcephaly, Mitochondrial myopathy, Muscle weakness, Nystagmus, Ophthalmoplegia, Optic atrophy, Optic disc pallor, Optic neuropathy, Paroxysmal involuntary eye movements, Peripheral neuropathy, Pigmentary retinopathy, Poor head control, Poor speech, Progressive cerebellar ataxia, Progressive macrocephaly, Progressive microcephaly, Progressive spastic paraplegia, Proximal tubulopathy, Ptosis, Reduced eye contact, Respiratory insufficiency, Seizure, Sensorineural hearing impairment, Skeletal muscle atrophy, Spasticity, Strabismus, Ventricular septal defect, Vomiting