Pyrenochaeta unguis-hominis-associated fungal keratitis: A rare case report with in vivo confocal microscopy findings

Purpose

Pyrenochaeta unguis-hominis, also known as Neocucurbitaria unguis-hominis, is a rare fungal pathogen typically isolated from skin and nail infections. Recently, it has been identified as a cause of fungal keratitis, particularly among contact lens wearers. This case report documents the occurrence of Pyrenochaeta unguis-hominis keratitis in Austria and the visualization of changes in the corneal stroma using in vivo confocal microscopy (IVCM).

Observations

A 48-year-old female patient presented with severe photophobia and acute pain in her left eye, following extended wear of soft contact lenses. Initial examination revealed a central corneal infiltrate. IVCM was performed prior to corneal scraping, which was then sent for direct staining, culture, and next-generation sequencing (NGS) and identified Pyrenochaeta unguis-hominis and Streptococcus oralis. Treatment included hourly topical voriconazole 2 %, natamycin 5 % and vancomycin 2.5 %, with additional epithelial debridement to enhance drug penetration. IVCM imaging allowed for real-time visualization and tracking of structures with the appearance of fungal hyphae, guiding the treatment course. Over several months, IVCM demonstrated a reduction in these structures, and the patient's condition stabilized, resulting in improved corneal clarity and Best Corrected Distance Visual Acuity from 0.8 to 0.9 (Snellen decimal scale).

Conclusions and importance

This case contributes to the limited clinical literature on Pyrenochaeta unguis-hominis-associated keratitis and includes IVCM imaging of a cornea with this rare infection. While IVCM provided early, non-invasive visualization of stromal changes, definitive diagnosis was achieved through molecular testing. A conservative treatment regimen with topical antifungals and epithelial debridement was effective, emphasizing the importance of rapid diagnostics and targeted therapy in managing rare corneal infections.