Abnormality of eye movement, Abnormality of movement, Abnormality of thalamus morphology, Abnormality of the cardiovascular system, Abnormality of the respiratory system, Acidosis, Acute necrotizing encephalopathy, Anemia, Apnea, Arrhythmia, Ataxia, Axial hypotonia, Babinski sign, Basal ganglia gliosis, Bilateral ptosis, Blindness, Blurred vision, Brain atrophy, Cardiac conduction abnormality, Central hypoventilation, Central retinal vessel vascular tortuosity, Central scotoma, Centrocecal scotoma, Cerebellar atrophy, Cerebral edema, Chorea, Coma, Congestive heart failure, Decreased activity of mitochondrial complex I, Decreased activity of mitochondrial respiratory chain, Decreased activity of the pyruvate dehydrogenase complex, Decreased liver function, Developmental regression, Diabetes mellitus, Diffuse white matter abnormalities, Dilated cardiomyopathy, Dysarthria, Dyskinesia, Dysphagia, Dystonia, Elevated brain lactate level by MRS, Emotional lability, Encephalopathy, Exercise intolerance, Failure to thrive, Feeding difficulties, Feeding difficulties in infancy, Fetal distress, Fluctuations in consciousness, Focal T2 hyperintense basal ganglia lesion, Focal T2 hyperintense brainstem lesion, Generalized hypotonia, Global brain atrophy, 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, Infantile muscular hypotonia, Intellectual disability, Intellectual disability, severe, Intrauterine growth retardation, Involuntary movements, Lactic acidosis, Leber optic atrophy, Lethargy, Leukodystrophy, Leukoencephalopathy, Limited extraocular movements, Mental deterioration, Microcephaly, Mitochondrial myopathy, Mitochondrial respiratory chain defects, Mitral regurgitation, Muscle weakness, Myopathy, Neurodevelopmental delay, Neuronal loss in basal ganglia, Nystagmus, Ophthalmoplegia, Optic atrophy, Optic disc pallor, Optic neuropathy, Paroxysmal involuntary eye movements, Peripheral neuropathy, Pigmentary retinopathy, Polyneuropathy, Poor eye contact, Poor head control, Poor suck, Postural tremor, Progressive cerebellar ataxia, Progressive macrocephaly, Progressive spastic paraplegia, Proximal tubulopathy, Ptosis, Pulmonic stenosis, Renal agenesis, Renal dysplasia, Renal tubular acidosis, Respiratory distress, Respiratory insufficiency, Retinal telangiectasia, Retinal vascular tortuosity, Retinopathy, Seizure, Sensorineural hearing impairment, Skeletal muscle atrophy, Slow decrease in visual acuity, Spasticity, Strabismus, Ventricular preexcitation, Ventricular septal defect, Ventriculomegaly, Visual impairment, Visual loss, Vomiting