Crohn病に合併した栄養欠乏性視神経症が疑われた1例

Suspected nutritional optic neuropathy in a case of Crohn disease

　20歳男性が5週間前からの両眼の羞明と視力低下で受診した。5年前にCrohn病と診断され，栄養剤などを服用し低脂肪低残さ性の食事をとっていた。矯正視力は右0.3，左0.5で，両眼に中心暗点があり，中心フリッカ値は測定不能であった。軽度の乳頭浮腫が両眼にあり，蛍光眼底造影で乳頭に軽い過蛍光があった。磁気共鳴画像検査（MRI）で頭部に異常はなかった。臨床所見と経過，Crohn病の既往などからビタミンB欠乏を含む栄養障害性視神経症が疑われた。ビタミンB₁₂の内服と筋注を開始し，16日後に視力，視野が大幅に改善した。消化器疾患に続発した栄養障害性視神経症が，視力低下の原因であると推定された1例である。

　A 20-year-old man presented with bilateral photophobia and blurring since 5 weeks before. He had been diagnosed with Crohn disease 5 years before. He had been treated with systemic nutritional supplements. His meals consisted of low-fat food with minimum residual substance. His corrected visual acuity was 0.3 right and 0.5 left. Both eyes showed central scotoma. Central flicker fusion was nonrecordable. Both eyes showed moderate disc edema with matching findings by fluorescein angiography. Magnetic resonance imaging（MRI）showed no intracranial abnormalities. The clinical findings and history of Crohn disease were suggestive of nutritional optic neuropathy including vitamin B₁₂deficiency. Systemic vitamin B₁₂was followed by remarkable improvement of visual acuity and field 16 days later. This case illustrates that nutritional optic neuropathy may develop secondary to gastrointestinal disorders.