BACKGROUND: Pythium insidiosum keratitis is a rare but sight-threatening disease with a high morbidity rate. It can be misdiagnosed as fungal keratitis in clinic settings. We report a case of severe Pythium insidiosum keratitis in a Chinese child, treated with combined approaches.

CASE REPORT: A 7-year-old boy from Hainan province in the south of China developed a suppurative corneal ulcer after being in a forest. A mass of hyphae was detected by confocal imaging in vivo, fungal smear test, and histochemical examination. Treatment with Natamycin, fluconazole, and Voriconazole for 1 month was unsuccessful, and a penetrating keratoplasty with anterior vitrectomy was performed. The infection reappeared 1 day after surgery, immediately after which anterior chamber irrigation with 0.02% Fluconazole and amphotericin B solution was performed. Finally, the globe was saved and there was no further recurrent infection. A cultured mycelial organism, which was hard to identify by biomorphology, was confirmed by PCR to be Pythium insidiosum. The zoospores were observed in water environments. The imaging characteristics of P. insidiosum in confocal microscopy are described herein.

CONCLUSIONS: This is the first case of Pythium insidiosum keratitis reported in China. It can be misdiagnosed as fungal keratitis in the clinic. Improving the awareness of clinicians, promoting early diagnosis, and a multidisciplinary approach, especially early surgery, improve the prognosis.

Keywords: Corneal Ulcer, Microscopy, Confocal, Oomycetes, Pythium