Nigrospora属糸状菌による遷延性真菌性角膜炎の1例

A case of persistent fungal keratitis caused by filamentous fungi belonging to Nigrospora spp.

要約　目的：Nigrospora属糸状菌による遷延性真菌性角膜炎の1例報告。

症例：69歳，男性。右眼を稲の葉で受傷し，近医で右角膜潰瘍と診断された。抗菌薬点眼で一時改善するもその後悪化し，別の近医を経て，島根県立中央病院へ紹介となった。入院による抗菌点眼薬治療で上皮欠損は残存していたが，前房炎症は改善したため退院した。しかし，その後に上皮欠損の拡大，前房炎症増悪を認め，鳥取大学医学部附属病院へ受診となった。植物外傷後であること，抗菌点眼薬使用下での再燃であることから真菌感染を考慮し，抗真菌薬を投与したところ，改善を認めた。培養開始後3週間でNigrospora属糸状菌を検出した。

結論：Nigrospora属糸状菌は黒色真菌の1菌種であり，環境に広く分布する。病原性は通常ないとされ，角膜炎の原因となったという報告は筆者らが知る限りでは1例のみである。今回分離された菌は非常に増殖力が弱く，そのため，寛解と増悪を繰り返し，診断が困難であったが，逆に病巣搔爬とホストの免疫力によって治癒したのではないかと考えられた。

Abstract　Purpose：To report a case of persistent fungal keratitis caused by filamentous fungi belonging to Nigrospora spp.

Case report：A 69-year-old man was injured in his right eye due to a rice plant. A local practitioner diagnosed the patient with bacterial corneal ulcer in his right eye and treated him with antibiotic instillation. However, after temporary improvement, his condition continued to worsen. He was referred to Shimane Prefectural Central Hospital by another local practitioner. Antibiotic treatment at the hospitalization had led to symptom improvement, except the corneal epithelial defect. However, due to the recurrence of anterior chamber inflammation and enlargement of the corneal epithelial defect, he was further referred to Tottori University Hospital. Fungal keratitis was suspected because of the occurrence of the symptoms after the rice plant injury and its recurrence despite antibiotic treatment. His corneal lesion improved after the commencement of antifungal treatment. Three weeks later, filamentous fungi belonging to Nigrospora spp. were detected from the culture of corneal scrapings.

Conclusions：Nigrospora is one of dematiaceous fungi and broadly distributed in the environment and considered as a non-pathogenic fungi. As far as we know, only 1 case of keratitis has been reported. Since the detected fungus in our case was very slow growing, remission and exacerbation occurred, resulting in difficult diagnosis. In contrast, its characteristic feature led to disease resolution by curettement and host immunity.