Corneal infections, particularly fungal keratitis due to rare fungal species, pose a diagnostic and therapeutic challenge because of difficulty in identification and varying susceptibility profiles. In this study, we report the first case of fungal keratitis because of Exophiala phaeomuriformis.
We report the clinical findings and microbial identification techniques of a case of fungal keratitis due to E. phaeomuriformis. An 84-year-old woman presented with redness, pain, and itching in the left eye for 2 weeks. Slit-lamp biomicroscopy revealed one broken suture from previous penetrating keratoplasty (PKP), black infiltrates at the 4-o'clock position, without an overlying epithelial defect and hypopyon. Microbial identification was based cultures on Sabouraud dextrose agar and DNA sequencing and correlations to laser in vivo confocal microscopy (IVCM; Heidelberg Retinal Tomograph 3/Rostock Cornea Module, Heidelberg Engineering) and multiphoton microscopy (Ultima Microscope; Prairie Technologies) images.
Slit-lamp biomicroscopy revealed one broken suture from previous PKP, black infiltrates at the 4-o'clock position, without an overlying epithelial defect and hypopyon. Based on a clinical suspicion of fungal keratitis, antifungals and fortified antibiotics were started. However, the patient did not respond to therapy and required urgent PKP. After surgery, the patient was maintained on topical and systemic voriconazole and also topical 2% cyclosporine for 5 months because of possibility of scleral involvement noticed during surgery. At the end of the treatment period, her vision improved from hand motion to 20/40, with no recurrence observed in a follow-up period of 1 year. Results of diagnostic tests were supported by fungal elements in stroma on IVCM. Culture from the infiltrate grew black yeast. DNA sequencing led to the diagnosis of E. phaeomuriformis keratitis. Antifungal susceptibility testing revealed sensitivity to voriconazole.
This is, to our knowledge, the first reported case of E. phaeomuriformis fungal keratitis. Diagnostic testing included slit-lamp biomicroscopy, which revealed pigmented infiltrates, culture plates grew black yeast, microscopy showed branched fungal hyphae with budding conidia, and physiological features showed tolerance to high temperatures, nitrate assimilation, and ribosomal DNA sequencing. Collectively, these tests demonstrate unique features seen for this microorganism. High suspicion should be kept with pigmented infiltrates and with dark yeast on culture plates. Prompt and aggressive medical management with voriconazole or therapeutic PKP in nonresponsive cases is essential to prevent irreversible loss of vision.