Nigrospora oryzae keratitis: a rare fungal etiology

To report a rare case of fungal keratitis caused by Nigrospora oryzae in an immunocompetent patient without a history of ocular trauma, and to compare its clinical and microbiological features with a previously published case.

A 62-year-old female farmer presented in December 2019 with a two-week history of ocular pain, redness, and visual loss in the right eye. Initial treatment by a local provider was unsuccessful. On presentation, slit-lamp examination revealed a raised central corneal infiltrate with feathery margins, associated with corneal neovascularization and hypopyon, but without epithelial defect. Corneal scraping was performed, and the specimen was analyzed by fungal staining, culture, and DNA sequencing.

Staining revealed septate hyphae, suggestive of a filamentous fungus. Culture confirmed Nigrospora oryzae with susceptibility to amphotericin B, itraconazole, and fluconazole. The patient was treated with oral itraconazole, topical amphotericin B 0.15%, and fortified povidone-iodine 5%. Complete resolution was achieved without recurrence, but with residual central scarring. No prophylactic antibiotics or corticosteroids were used. A comparative review with the only other reported case revealed differences in ulcer characteristics, treatment protocols, and antifungal susceptibility.

Nigrospora oryzae is a rare cause of fungal keratitis that can present in immunocompetent individuals without apparent trauma. In resource-limited settings like Vietnam, delayed diagnosis due to limited microbiological support may obscure detection of uncommon pathogens. This case underscores the need for enhanced diagnostic capacity and awareness of atypical fungal agents in cases of infectious keratitis.