シスチノーシスによる特徴的な角膜混濁を認めた2症例

Characteristic corneal opacity in two cases of cystinosis

要約　目的：常染色体劣性のライソゾーム病であるシスチノーシスに伴う角膜混濁において，前眼部光干渉断層計（AS-OCT）が有用であった2症例の報告。

対象と方法：症例1は17歳，男性。12歳でファンコーニ症候群と，角膜混濁から中間型（腎障害が軽症な病型）のシスチノーシスと診断された。症例2は32歳，男性。2歳でファンコーニ症候群と腎不全の精査により，腎障害型（腎障害が重症な病型）シスチノーシスと診断された。2症例に対しAS-OCTを用いて，角膜の輝度反射の分布を角膜中央部から1mm，2mmの4か所で測定した。

結果：2症例ともに細隙灯顕微鏡検査で特徴的な角膜混濁を認めた。AS-OCTでは顆粒状の輝度反射の分布が観察され，症例1では，すべての測定点で角膜深度と輝度反射に負の相関（r＝−0.31〜−0.68）があった（p＜0.05）。一方，症例2では，内皮側に反射が強い1か所で正の相関（r＝0.36，p＜0.05）があり，他の測定点では有意な相関はなかった。

結論：シスチノーシスによる角膜混濁がある2症例で，AS-OCTで顆粒状の輝度反射が観察された。これまで定量的な眼科的診断が報告されていない本疾患に対して，前眼部OCTによる評価が有用であることが示された。

Abstract　Purpose：To report cases of two patients who were clinically diagnosed with cystinosis—an autosomal recessive lysosomal storage disorder—in whom the corneal opacities were examined using the anterior segment optical coherence tomography（AS-OCT）.

Objects and Methods：Case 1 involves a 17-year-old man with the nephropathic juvenile form of cystinosis who was diagnosed with the disease and the Fanconi syndrome along with corneal opacities at the age of 12；he showed a slower progression to the end-stage renal disease（mild type）. Case 2 involves a 32-year-old man with nephropathic infantile form of the disease who was diagnosed with the disease and the Fanconi syndrome as well as with severe renal failure at the age of 2 years；the patient progressed to the end-stage renal disease in the first decade of life（severe type）. In each case, the average of the image intensity value obtained using AS-OCT on the one-pixel from the corneal epithelium to the endothelium at the distance of 1 mm or 2 mm from the center of the cornea was determined.

Result：In both cases, the characteristic corneal opacity associated with cystinosis was observed by slit-lamp-microscopic examination. Using the AS-OCT, the accumulation of granular cystine crystals was observed as corneal reflex intensity. In Case 1, a negative relationship（r＝−0.31 to−0.68）was observed in the corneal depth and reflex intensity in all areas measured（p＜0.05）, whereas in Case 2, excepting one area, no significant differences were observed in the relationship（r＝0.36, p＜0.05）.

Conclusion：Two cases with cystinosis with the characteristic corneal opacities were examined using AS-OCT, and the accumulation of granular corneal reflex intensity was observed in the corneal layer of these patients. AS-OCT examination is useful to quantitatively estimate the characteristic corneal opacities associated with cystinosis.