Coma, Confusion, Craniofacial dystonia, Decreased activity of mitochondrial respiratory chain, Decreased activity of the pyruvate dehydrogenase complex, Downslanted palpebral fissures, Drowsiness, Dysarthria, Dysphagia, Dystonia, Emotional lability, Encephalopathy, External ophthalmoplegia, Failure to thrive, Fever, Focal T2 hyperintense basal ganglia lesion, Functional motor deficit, Gait ataxia, Global developmental delay, Hearing impairment, Hyperreflexia, Hypertrichosis, Hypertrophic cardiomyopathy, Hypotonia, Inability to walk, Inappropriate crying, Increased CSF lactate, Increased circulating lactate concentration, Infantile encephalopathy, Infantile muscular hypotonia, Infantile spasms, Intellectual disability, severe, Irritability, Leukodystrophy, Loss of consciousness, Morphological abnormality of the pyramidal tract, Mutism, Nystagmus, Ophthalmoplegia, Optic atrophy, Paraparesis, Peripheral neuropathy, Pigmentary retinopathy, Poor speech, Progressive cerebellar ataxia, Progressive spastic paraplegia, Psychomotor retardation, Ptosis, Respiratory insufficiency, Restlessness, Rigidity, Seizure, Small basal ganglia, Spastic tetraplegia, Spasticity, Status epilepticus, Strabismus, Tetraparesis, Ventricular septal defect