Abnormal activity of mitochondrial respiratory chain, Abnormal emotion/affect behavior, Abnormal fear/anxiety-related behavior, Abnormal hair quantity, Abnormality of acid-base homeostasis, Abnormality of body height, Abnormality of body weight, Abnormality of cell physiology, Abnormality of central motor function, Abnormality of coordination, Abnormality of eye movement, Abnormality of higher mental function, Abnormality of metabolism/homeostasis, Abnormality of mitochondrial metabolism, Abnormality of movement, Abnormality of muscle fibers, Abnormality of muscle morphology, Abnormality of muscle physiology, Abnormality of pyramidal motor function, Abnormality of skin adnexa, Abnormality of the cardiovascular system, Abnormality of the central nervous system, Abnormality of the cerebellum, Abnormality of the cerebrospinal fluid, Abnormality of the cerebrum, Abnormality of the eye, Abnormality of the forebrain, Abnormality of the fundus, Abnormality of the glial cells, Abnormality of the hair, Abnormality of the heart, Abnormality of the hindbrain, Abnormality of the integument, Abnormality of the lung, Abnormality of the metencephalon, Abnormality of the mitochondrion, Abnormality of the musculature, Abnormality of the myocardium, Abnormality of the nervous system, Abnormality of the optic nerve, Abnormality of the posterior segment of the eye, Abnormality of the respiratory system, Abnormality of the retina, Abnormal mitochondria in muscle tissue, Abnormal muscle tone, Abnormal pattern of respiration, Acidosis, Age of onset, All, Ataxia, Autosomal recessive inheritance, Babinski sign, Behavioural/Psychiatric Abnormality, Cardiomyopathy, Cognitive impairment, Decreased activity of mitochondrial complex II, Decreased activity of mitochondrial respiratory chain, Decreased body weight, Dysarthria, Dystonia, Emotional lability, Exercise intolerance, Failure to thrive, Functional motor problems., Functional respiratory abnormality, Gliosis, Growth abnormality, Growth delay, Heterogeneous, Hyperreflexia, Hypertonia, Hypertrichosis, Hypertrophic cardiomyopathy, Increased CSF lactate, Infantile onset, Intellectual disability, Involuntary movements, Lactic acidosis, Leukoencephalopathy, Malformation of the heart and great vessels, Mitochondrial inheritance, Mode of inheritance, Morphological abnormality of the central nervous system, Muscle weakness, Muscular hypotonia, Myoclonus, Neonatal hypotonia, Neurological speech impairment, Nystagmus, Onset, Onset and clinical course, Ophthalmoparesis, Ophthalmoplegia, Optic atrophy, Pace of progression, Phenotypic abnormality, Phenotypic variability, Pigmentary retinopathy, Progressive disorder, Progressive leukoencephalopathy, Ragged-red muscle fibers, Respiratory insufficiency, Seizures, Short stature, Spasticity, Stress/infection-induced lactic acidosis.