Defects in MT-ATP6 are the cause of neurogenic muscle weakness, ataxia, and retinitis pigmentosa (NARP) . Defects in MT-ATP6 are a cause of Leber hereditary optic neuropathy (LHON). LHON is a maternally inherited disease resulting in acute or subacute loss of central vision, due to optic nerve dysfunction. Cardiac conduction defects and neurological defects have also been described in some patients. LHON results from primary mitochondrial DNA mutations affecting the respiratory chain complexes. Defects in MT-ATP6 are a cause of Leigh syndrome (LS). LS is a severe neurological disorder characterized by bilaterally symmetrical necrotic lesions in subcortical brain regions.Defects in MT-ATP6 are a cause of infantile bilateral striatal necrosis . Bilateral striatal necrosis is a neurological disorder resembling Leigh syndrome.