胸腺腫の経過観察中に夕焼け状眼底を呈した1例

A case of sunset-glow fundus during treatment for thymoma

要約　目的：胸腺腫の治療中に夕焼け状眼底が生じた症例の報告。症例：56歳女性が視力低下で受診した。10年前に重症筋無力症を伴う胸腺腫と診断され，胸腺摘出と化学療法が行われた。2年前に胸腺腫が再発し，シクロスポリンとプレドニゾロン投与を開始した翌日に全身の脱毛と皮膚の脱色素が生じた。その3か月後には眼底は正常であったが，さらに7か月後に両眼が夕焼け状眼底になった。所見：視力は右1.2，左1.0であり，両眼に夕焼け状眼底と黄斑変性があった。光干渉断層計で中心窩の網膜色素上皮に高反射があった。以後16か月の経過中，周辺から眼底中央部に向かう色素沈着が生じた。剖検で脈絡膜のメラノサイト脱落はなかった。結論：本症例の夕焼け状眼底は，原疾患または長期の薬剤投与で生じたメラノサイトに対する自己免疫による可能性がある。

Abstract.　Purpose：To report a case who developed sunset-glow fundus during treatment for thymoma. Case：A 56-year-old female presented with blurring of vision. She had been diagnosed as thymoma with myasthenia gravis 10 years before and received excision of thymus and chemotherapy. Thymoma recurred 2 years before. Generalized alopecia and skin depigmentation developed on day 2 of treatment with systemic cyclosporine and prednisolone. She had reportedly no fundus depigmentation 3 months later but showed sunset-glow fundus another 7 months later. Findings：Her visual acuity was 1.2 right and 1.0 left. Both eyes showed sunset-glow fundus with macular degeneration. Optical coherence tomography showed a high reflection from the retinal pigment epithelium in the fovea. Pigment patches started to appear in the peripheral fundus during the follow-up of 16 months. Autopsy showed no abnormal melanocytes in the choroid. Conclusion：Sunset-glow fundus may have been induced by autoimmunity to melanocytes due to thymoma or medication.