BACKGROUND The utility of formalin-fixed paraffin-embedded (FFPE) corneal tissue specimens for retrospective diagnosis of microsporidial keratitis was evaluated by transmission electron microscopy (TEM) analysis and the possible second case of microsporidial keratitis after Descemet stripping automated endothelial keratoplasty (DSAEK) was described. CASE PRESENTATION A 68-year-old man presented with multiple crystalline opacities in the corneal stroma that progressed extremely slowly after DSAEK. Fungiflora Y staining of corneal scrapings from the affected regions revealed an oval microorganism. Topical voriconazole administration was ineffective and penetrating keratoplasty was performed. Histological and molecular analyses were carried out on the excised cornea. Ziehl-Neelsen staining revealed an acid-fast, oval organism that was visible by ultraviolet illumination after Fungiflora Y and Uvitex 2B staining, whereas periodic acid-Schiff and Grocott's staining did not yield any significant findings. Microsporidium was detected by TEM of FFPE tissue. Nosema or Vittaforma sp. was suspected as the causative microorganism by PCR of FFPE tissue and by the fact that those species are known to cause eye infection. The corneal graft has maintained transparency at 1 year and half postoperatively. CONCLUSIONS This is the first known case of microsporidial keratitis diagnosed retrospectively by molecular and ultrastructural study of FFPE tissue, and the possible second case of microsporidial keratitis after DSAEK. Microsporidial keratitis should be considered when corneal opacity refractory to conventionally known therapy would occur after DSAEK. Our findings suggest that more microsporidial keratitis cases than have been reported to date can be identified by TEM or PCR examination of FFPE corneal specimens.

中文翻译：

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通过福尔马林固定石蜡包埋的角膜组织的超微结构研究回顾性诊断为微孢子性角膜炎：一例。

背景技术通过透射电镜（TEM）分析评估了福尔马林固定石蜡包埋（FFPE）角膜组织标本在微孢子菌性角膜炎的回顾性诊断中的作用，以及在Descemet剥离自动内皮角膜移植术（DSAEK）后可能发生的第二例微孢子性角膜炎。描述。病例介绍一名68岁的男子在角膜基质中出现多种晶体混浊，DSAEK后进展非常缓慢。来自患病区域的角膜刮屑的真菌Y染色显示为椭圆形微生物。伏立康唑的局部给药无效并且进行了穿透性角膜移植术。在切除的角膜上进行组织学和分子分析。Ziehl-Neelsen染色显示耐酸，椭圆形生物，在真菌X和Uvitex 2B染色后通过紫外线照射可见，而高碘酸席夫和格罗科特染色未见任何明显发现。通过FFPE组织的TEM检测微孢子虫。Nosema或Vittaforma sp。通过FFPE组织的PCR以及已知这些物种会引起眼部感染的事实，该细菌被怀疑是病原微生物。角膜移植物在术后一年半时保持透明。结论这是通过FFPE组织的分子和超微结构研究回顾性诊断的第一例微孢子性角膜炎病例，也是DSAEK后第二例可能的微孢子性角膜炎病例。当DSAEK后发生传统上难以治愈的角膜混浊时，应考虑微孢子性角膜炎。