輪部から発生した再発性角膜上皮混濁の1例

A case of recurrent corneal epithelial opacity originating from the limbus

　角膜上皮の幹細胞は輪部に存在し，輪部から供給された上皮細胞は角膜中央部に向かって移動するとされている（XYZ理論）。このような角膜上皮細胞の維持に関して示唆を与えてくれる症例を経験した。症例は33歳男性。初診時，右眼に特異な形態をした角膜上皮混濁を認め，その一部は2時方向の輪部に達していた。混濁上皮を擦過したが，2年後には初診時と同じ形態で再発していた。再度擦過したが，その後，輪部より混濁上皮が角膜中央部に移動するのが認められた。混濁上皮は組織学的には細胞壊死の状態であった。混濁上皮の動きは，恒常状態の角膜上皮細胞の動態をある程度反映したものと考えられた。

Stem cells of corneal epithelium are thought to be located in the limbal area and to slowly replicate sending their daughter cells towards the central cornea. This centripetal movement corresponds to the Y axis according to the XYZ hypothesis by Thoft & Friend. We observed a case which seemed to support this concept.

A 33-year-old male presented with recurrent corneal epithelial opacity in his right eye. The opacity was located at 2 o'clock position and was composed of two parts: a round opacity towards the center and a linear peripheral opacity, simulating a tadpole. We treated the eye by mechanical scraping. After the cornea became transparent, an identical lesion recurred 2 years later manifesting the tadpole appearance. Another scraping of the lesion was followed by similar recurrence one year later. The scraped material contained layered and necrotic epithelial cells. The centripetal movement of corneal epithelium could be observed in this case because abnormal epithelial cells acted as if they were labelled by a sort of cell markers.