Abnormality of mitochondrial metabolism, Abnormality of neuronal migration, Abnormality of retinal pigmentation, Abnormality of the dentition, Abnormality of visual evoked potentials, Acute necrotizing encephalopathy, Amaurosis fugax, Anorexia, Anterior hypopituitarism, Anxiety, Aortic aneurysm, Aortic dissection, Aphasia, Aplasia/Hypoplasia of the cerebellum, Apnea, Arrhythmia, Arthrogryposis multiplex congenita, Ataxia, Attention deficit hyperactivity disorder, Autism, Babinski sign, Bilateral sensorineural hearing impairment, Bilateral tonic-clonic seizure, Blindness, Blurred vision, Bulbar signs, Cachexia, Cardiac conduction abnormality, Carious teeth, Cataract, Central retinal vessel vascular tortuosity, Central scotoma, Centrocecal scotoma, Cerebellar atrophy, Cerebral calcification, Cerebral cortical atrophy, Cerebral edema, Cerebral ischemia, Cerebral visual impairment, Chorea, Clonus, Cognitive impairment, Coma, Congestive heart failure, Constipation, Decreased activity of mitochondrial complex I, Decreased activity of mitochondrial respiratory chain, Decreased nerve conduction velocity, Delayed puberty, Delayed skeletal maturation, Dementia, Demyelinating peripheral neuropathy, Depression, Developmental cataract, Developmental regression, Diabetes mellitus, Dilated cardiomyopathy, Dysarthria, Dyskinesia, Dysphagia, Dyspnea, Dystonia, EEG abnormality, EMG abnormality, Elevated circulating creatine kinase concentration, Encephalopathy, Episodic respiratory distress, Episodic vomiting, Exercise intolerance, Failure to thrive, Fatigue, Feeding difficulties, Feeding difficulties in infancy, Fetal distress, Fever, Focal T2 hyperintense basal ganglia lesion, Focal T2 hyperintense brainstem lesion, Gait ataxia, Gastroparesis, Generalized hirsutism, Generalized hypotonia, Generalized myoclonic seizure, Gingival overgrowth, Global developmental delay, Glomerulopathy, Goiter, Growth abnormality, Growth delay, Hallucinations, Heart block, Hemianopia, Hemiparesis, Hepatic failure, Hepatomegaly, Hyperalaninemia, Hypercalciuria, Hyperreflexia, Hypertelorism, Hypertension, Hyperthyroidism, Hypertrophic cardiomyopathy, Hyperventilation, Hypoglycemia, Hypoparathyroidism, Hypopigmented skin patches, Hyporeflexia, Hypothermia, Hypothyroidism, Hypotonia, Ichthyosis, Increased CSF lactate, Increased circulating lactate concentration, Increased serum pyruvate, Infantile muscular hypotonia, Infantile spasms, Intestinal obstruction, Intrauterine growth retardation, Lactic acidosis, Lacticaciduria, Leber optic atrophy, Left ventricular hypertrophy, Lethargy, Leukodystrophy, Leukoencephalopathy, Low plasma citrulline, Malabsorption, Mask-like facies, Memory impairment, Microcephaly, Migraine, Mitochondrial myopathy, Mitochondrial respiratory chain defects, Multiple glomerular cysts, Multiple lipomas, Muscle weakness, Myalgia, Myopathy, Nausea and vomiting, Nephrotic syndrome, Neurological speech impairment, Nyctalopia, Nystagmus, Ophthalmoparesis, Ophthalmoplegia, Optic atrophy, Optic disc pallor, Optic neuropathy, Pancreatitis, Paresthesia, Paroxysmal involuntary eye movements, Peripheral neuropathy, Pigmentary retinopathy, Polyneuropathy, Poor eye contact, Poor head control, Postural tremor, Primary adrenal insufficiency, Progressive macrocephaly, Progressive sensorineural hearing impairment, Proteinuria, Protruding ear, Proximal tubulopathy, Psychotic episodes, Ptosis, Pulmonary arterial hypertension, Pulmonary embolism, Ragged-red muscle fibers, Reduced consciousness/confusion, Reduced tendon reflexes, Renal insufficiency, Respiratory insufficiency, Retinal telangiectasia, Retinal vascular tortuosity, Rod-cone dystrophy, Segmental peripheral demyelination/remyelination, Seizure, Sensorimotor neuropathy, Sensorineural hearing impairment, Severe global developmental delay, Short stature, Skeletal muscle atrophy, Slow decrease in visual acuity, Spasticity, Spontaneous hematomas, Strabismus, Stroke-like episode, Sudden cardiac death, Thyroiditis, Tremor, Type I diabetes mellitus, Type II diabetes mellitus, Ventricular preexcitation, Ventriculomegaly, Visual field defect, Visual impairment, Visual loss, Vomiting, Wolff-Parkinson-White syndrome