Not Fungal After All: The Diagnostic Puzzle of Pythium Keratitis – First Case Report from Pakistan

Doi: 10.36351/pjo.v42i3.2270

Abstract

Pythium keratitis, caused by the oomycete Pythium insidiosum, is a rare and emerging cause of vision-threatening corneal ulcers. Clinically, it mimics fungal keratitis but is unresponsive to conventional antifungal therapy.Microbiologically confirmed cases have been rarely reported from Pakistan. A corneal scraping from a patient under antifungal therapy for presumed fungal keratitis was submitted for microbiological evaluation. Inoculation onto blood agar and Mueller Hinton agar with 10% KOH and Lactophenol Cotton Blue (LCB) staining revealed white colonies. Microscopy demonstrated hyphae, sporangia, sporangiophores, and sporangiospores, confirming Pythium insidiosum. The corneal abscess leads to perforation for which emergency sclero-conjunctival flap was performed; however, this incidental finding highlights the importance of suspecting Pythium in refractory corneal ulcers.Ophthalmologists should consider corneal scrapings in non-responsive cases and recognize characteristic tentacle-shaped stromal infiltrates to guide early diagnosis and management.