Crohn病に続発しビタミンA投与が奏効した後天夜盲

Peroral vitamin A was effective for night blindness in a case of Crohn's disease

要約　目的：Crohn病に併発した夜盲にビタミンA投与が奏効した症例の報告。症例：38歳女性が夜盲を主訴として受診した。22年前にCrohn病が発症し，寛解と増悪を繰り返し，低栄養状態が続いていた。矯正視力は左右眼とも1.2であり，眼底に点状の小灰白色斑が多発していた。網膜電図（ERG）はa波とb波が著明に減弱し，暗順応曲線が第1相，第2相ともに平坦化していた。血中ビタミンA値が著しく低下していた。ビタミンA欠乏による特発性夜盲と診断した。結果：ビタミンA投与を開始し，2週間後に夜盲を自覚しなくなった。ERGと暗順応曲線は5か月後にほぼ正常化し，眼底の小灰白色斑もほぼ消失した。結論：本症例はCrohn病に伴う消化管吸収障害でビタミンA欠乏が続発して夜盲が生じたと解釈され，ビタミンAの経口投与が著効を示した。

Abstract.　Purpose：To report a case of Crohn's disease with night blindness that was cured by peroral vitamin A. Case：A 38-year-old woman presented with night blindness as chief complaint. She had been diagnosed with Crohn's disease 22 years ago. She was in a state of poor nourishment after improvements and exacerbations of the disease. Her corrected visual acuity was 1.2 in either eye. Funduscopy showed diffuse gray-white spots. Electroretinogram showed severely attenuated a and b waves. Dark adaptation curve was flattened in the first and second phases. Serum level of vitamin A was extremely low. Results：Night blindness disappeared after 2 weeks of treatment with peroral vitamin A. Electroretinogram and dark adaptation became almost normal 5 months later. Gray-white spots in the fundus also disappeared. Conclusion：Night blindness in the present case was apparently due to malabsorption by Crohn's disease. Peroral vitamin A was effective for the night blindness.