増殖糖尿病網膜症および錐体ジストロフィを合併しRDH5遺伝子変異を認めた白点状眼底

Mutation of RDH5 gene in a case of fundus albipunctatus with cone dystrophy and proliferative diabetic retinopathy

要約　目的：白点状眼底に錐体ジストロフィと増殖糖尿病網膜症が併発した症例の報告。症例：幼少時から夜盲があり，9年前から糖尿病で加療中の42歳男性が眼科的診察を希望して受診した。両親は近親婚ではなく，2名の同胞に眼疾患はない。所見：視力は左右とも1.2で，両眼に黄斑の色調異常，後極部から周辺にかけて散在する無数の小白点と，単純糖尿病網膜症の所見があった。3年後に増殖糖尿病網膜症になり，汎網膜光凝固を行った。初診から8年後に網膜電図を検査し，錐体系と杆体系反応に振幅低下があった。3時間の暗順応で錐体系反応は変化せず，杆体系反応は著しく改善した。RDH5遺伝子の検査で，複合ヘテロ接合変異（R280H，L310delinsEV）があった。51歳時の視力は不変で，凝固斑の間にある白点は目立たなくなった。結論：本症例は錐体ジストロフィが併発した白点状眼底と診断される。増殖糖尿病網膜症と汎網膜光凝固により白点は消退する傾向を示した。

Abstract.　Purpose：To report a case of fundus albipunctatus associated with cone dystrophy and proliferative diabetic retinopathy（PDR）. Case：A 42-year-old male presented with history of diabetes mellitus since 9 years before. He had had night blindness since childhood. His parents were not consanguineous. Findings：Corrected visual acuity was 1.2 in either eye. Both eyes showed abnormal color of the macula,numerous white dots distributed from the posterior pole to the periphery,and findings of simple diabetic retinopathy. Both eyes received panretinal photocoagulation for PDR 3 years later. Electroretinography at the age of 50 years showed reduced cone and rod responses. After 3 hours of dark adaptation,cone response remained unchanged and rod response improved remarkably. Genetic analysis showed compound heterozygous mutation（R280H,L310delinsEV）in the RDH5 gene. Visual acuity at the age of 51 years remained unchanged. White dots in the fundus became less conspicuous in areas unaffected by photocoagulation. Conclusion：This case was diagnosed with fundus albipunctatus associated with cone dystrophy. White dots in the fundus showed a tendency to become less conspicuous after PDR and panretinal photocoagulation.