Because demyelinating disease could not explain the patient's clinical (simultaneous bilateral visual loss) andradiologic findings (unusual and atypical location of demyelinating plaques), genetic testing with targeted sequencing was performedin which the entire coding region of the genes MT -ATP6, MT -CO1, MT -CO3, MTCYB, MT -ND1, MT -ND2, MT -ND4, MTND4L, MT -ND5, and MT -ND6was amplified and sequenced (Next Generation Sequencing of Leber optic atrophy panel). The gene discussed is MCAT; the disease is optic atrophy.