Detrusor sphincter dyssynergia, Developmental regression, Diffuse cerebral atrophy, Dysarthria, Dystonia, EEG abnormality, Equinovarus deformity, Feeding difficulties, Feeding difficulties in infancy, Generalized hypotonia, Gliosis, Global developmental delay, Growth delay, Hearing impairment, Hip dysplasia, Hyperreflexia, Hypotonia, Impaired mastication, Increased circulating lactate concentration, Insomnia, Intention tremor, Kyphoscoliosis, Lactic acidosis, Loss of ambulation, Lower limb amyotrophy, Lower limb hyperreflexia, Lower limb spasticity, Macrodontia of permanent maxillary central incisor, Microcephaly, Muscle abnormality related to mitochondrial dysfunction, Myoclonus, Neurogenic bladder, Neuromuscular dysphagia, Paroxysmal dystonia, Poor head control, Profound global developmental delay, Progressive spastic paraplegia, Ptosis, Retrognathia, Scissor gait, Seizure, Spastic paraplegia, Strabismus, Sudden episodic apnea, Thrombocytopenia, Urinary incontinence, Ventriculomegaly, Visual impairment, Weakness due to upper motor neuron dysfunction