外傷性の左上同名四半盲の合併により診断に苦慮したLeber遺伝性視神経症の1例

A case of Leber hereditary optic neuropathy with traumatic homonymous quadrantanopia as the initial manifestation

要約　目的：同名四半盲を呈したLeber遺伝性視神経症の報告。症例：52歳男性が3か月前からの両眼の視力低下で受診した。17年前に交通事故による脳挫傷の既往があった。所見：矯正視力は右0.2，左0.15，対光反射は良好で，左上同名四半盲があった。明らかな視力低下の原因を認めず，機能的視覚障害も考慮し経過観察とした。初診から1年後，視力は両眼手動弁，対光反射は減弱し，両眼に視神経萎縮があった。遺伝子検査でミトコンドリアDNA11778変異があり，Leber遺伝性視神経症と診断した。結論：頭部外傷による両眼性視野障害を呈する症例に，原因不明の視力低下を認めた場合，Leber遺伝性視神経症の可能性も念頭に置き，遺伝子検査を考慮する必要がある。

Abstract.　Purpose：To report a case of Leber hereditary optic neuropathy（LHON）who showed homonymous quadrantanopia as the initial symptom. Case：A 52-year-old man presented with impaired vision in both eyes since 3 months before. He had had cerebral injury during traffic accident 17 years before. Findings：Corrected visual acuity was 0.2 right and 0.15 left. Pupillary light reflex was within normal limits. Both eyes showed left superior quadrantanopia. Because we could not clarify the cause of impaired vision, he was observed in consideration of the functional visual impirment. When seen one year after his initial visit, visual acuity decreased to hand motion in both eyes. Pupillary light reflex was incomplete in both eyes. Both eyes showed optic atrophy. Genetic analysis showed mitochondrial mutation at DNA11778, leading to the diagnosis of LHON. Conclusion：Genetic analysis for LHON should be considered in patients with impaired vision in both eyes of unknown cause.