A 20-year-old woman suffered from a persistent toenail infection that didn’t respond to several standard antifungal treatments over five years. Researchers identified the culprit as Yarrowia lipolytica, a rare yeast not previously known to cause nail infections. Testing showed this yeast was resistant to common antifungal medications the patient had received, explaining why previous treatments failed. This unusual case highlights the importance of properly identifying fungal pathogens and testing them for drug resistance before starting treatment.