遺伝子診断で確定した若年発症の金柑型膠様滴状角膜ジストロフィの1例

A case of young-onset kumquat-like type of gelatinous drop-like corneal dystrophy diagnosed by gene analysis

要約　目的：若年性の金柑型膠様滴状角膜ジストロフィの1例の報告。症例：38歳女性が両眼の強い眼痛で受診した。10歳時に両眼の視力低下と眼痛があり，両眼に角膜の隆起性混濁が指摘された。14歳時に左眼に角膜移植を受けた。両親はいとこ同士であった。所見：矯正視力は左右眼とも手動弁で，眼圧は右47mmHg，左37mmHgであった。両眼の角膜に血管侵入を伴う黄色の隆起があり，角膜後面よりも後方は不透明であった。臨床所見から金柑型膠様滴状角膜ジストロフィと診断した。遺伝子検査でTACSTD2遺伝子にc.632delA変異があった。両眼に角膜部分切除を行い，コンタクトレンズを装用させた。切除した角膜にアミロイドの沈着があった。矯正視力は右0.2，左0.1になり，眼圧は正常化した。結論：TACSTD2遺伝子のc.632delA変異が金柑型膠様滴状角膜ジストロフィに特異的であるという報告はない。本症が若年に発症した原因として，他の遺伝子の関与や環境要因が推定される。

Abstract.　Purpose：To report a case of young-onset kumquat-like type of gelatinous drop-like corneal dystrophy. Case：A 38-year-old female presented with severe ocular pain in both eyes as the chief complaint. She had impaired visual acuity and pain in both eyes at the age of 10 years, followed by detection of elevated lesion in the cornea. She had received penetrating keratoplasty at the age of 14 years. Her parents were cousins. Findings：Corrected visual acuity was hand motion in either eye. Intraocular pressure was 47 mmHg right and 37 mmHg left. Both eyes showed elevated yellow corneal lesion with neovascularization. The clinical findings were compatible with the diagnosis of kumquat-like type of gelatinous drop-like corneal dystrophy. Gene analysis showed c.632delA mutation in TACSTD2. Both eyes received keratectomy followed by soft contact lens wear. Visual acuity improved to 0.2 right and 0.1 left. Conclusion：There has been no report of c.632delA mutation in TACSTD2 associated with kumquat-like type of gelatinous drop-like corneal dystrophy. Other unidentified genetic or environmental factor may be involved as the cause of young onset of keratopathy.