強皮症による偽性腸閉塞からビタミンA欠乏性夜盲となった1例

A case of vitamin A deficiency night blindness due to pseudointestinal obstruction caused by scleroderma

要約　目的：強皮症による偽性腸閉塞からビタミンA欠乏性夜盲をきたした1例の報告。

症例：55歳，女性。半年前からの夜盲と視野狭窄感を訴え，内科より紹介された。矯正視力は右1.0，左1.0，眼底検査では両眼後極から周辺部にかけて顆粒状から斑状の大きさの異なる白斑が密にあり，眼底自発蛍光撮影では白斑に一致して淡い過蛍光斑を多数認めた。光干渉断層計（OCT）ではellipsoid zone（EZ）の不整とinterdigitation zoneの消失があり，網膜電図（ERG）ではフラッシュERGは陰性型で杆体ERGは消失していた。血清ビタミンA濃度は6IU/dlで，ビタミンA欠乏による夜盲と診断した。ビタミンAの経口投与を開始し1週間後には夜盲はほぼ消失し，治療開始6週間後のOCT所見ではEZは回復傾向で，ERGの波形は著明に改善した。治療開始1か月ごろから嘔気嘔吐や下痢が悪化したため，ビタミンAの内服を中止した後，筋肉注射に切り替えた。初診から1年2か月が経過した現在も症状の再燃はなく経過している。

結論：夜盲を訴え眼底に多数の白斑を認める患者を診た場合，続発性のビタミンA欠乏症の可能性を考え，詳細な病歴聴取を行うべきである。また，ビタミンA製剤の内服が困難な患者に対しては注射製剤の使用が有用と考える。

Abstract　Objective：To report a case of vitamin A deficient night blindness due to pseudointestinal obstruction caused by scleroderma.

Case：A 55-year-old female complaining of night blindness and tunnel vision for half a year was introduced by the internal medicine department. Her best-corrected visual acuity was 1.0 in both eyes. Fundus examination revealed dense white spots of different sizes, from granular to patchy in shape, located from the posterior pole to the periphery in both eyes, and many slightly hyperfluorescent spots were observed from the posterior pole to the periphery in the fundus autofluorescence images. Optical coherence tomography（OCT）showed irregularity in the ellipsoid zone and disappearance of the interdigitation zone. Electroretinogram（ERG）showed diminished amplitude, and serum vitamin A concentration was 6 IU/dl. She was diagnosed with night blindness due to vitamin A deficiency. Nyctalopia almost disappeared one week after the start of oral vitamin A administration, and an improvement of OCT and ERG findings was observed six weeks later. Because nausea, vomiting, and diarrhea worsened one month after the start of treatment, oral vitamin A was discontinued and switched to intramuscular injection. In the 14 months after the first visit, she had not relapsed.

Conclusions：When examining a patient who complains of night blindness and has a large number of white spots on the fundus, a detailed medical history should be conducted considering the possibility of secondary vitamin A deficiency. Intramuscular injection of vitamin A is considered to be useful in case of difficulty in orally taking vitamin A.