Cerebellar atrophy, Cerebral edema, Cerebral visual impairment, Coma, Decreased activity of mitochondrial complex I, Decreased activity of mitochondrial respiratory chain, Decreased activity of the pyruvate dehydrogenase complex, Delayed myelination, 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, Gait disturbance, Generalized hypotonia, Global developmental delay, Growth delay, Hearing impairment, Hepatic failure, Hepatomegaly, Hyperreflexia, Hypertrichosis, Hypertrophic cardiomyopathy, Hypoglycemia, Hyporeflexia, Hypotonia, Inability to walk, Increased CSF lactate, Increased circulating lactate concentration, Increased serum pyruvate, Intellectual disability, severe, Intrauterine growth retardation, Lactic acidosis, Lethargy, Leukodystrophy, Leukoencephalopathy, 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, Poor speech, Progressive cerebellar ataxia, Progressive macrocephaly, Progressive spastic paraplegia, Proximal tubulopathy, Ptosis, Respiratory insufficiency, Rigidity, Scoliosis, Secondary microcephaly, Seizure, Sensorineural hearing impairment, Skeletal muscle atrophy, Spasticity, Strabismus, Ventricular septal defect, Ventriculomegaly, Vomiting