MTND2 belongs to the complex I subunit 2 family. Defects in MT-ND2 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-ND2 may be associated with susceptibility to Alzheimer disease mitochondrial (AD-MT) . Alzheimer disease is a neurodegenerative disorder characterized by progressive dementia, loss of cognitive abilities, and deposition of fibrillar amyloid proteins as intraneuronal neurofibrillary tangles, extracellular amyloid plaques and vascular amyloid deposits.