Abstract
BACKGROUND AND PURPOSE: Onychomycosis is predominantly caused by dermatophytes; however, non-dermatophytic molds are emerging as opportunistic pathogens. These infections pose diagnostic and therapeutic challenges due to their rarity, variable drug susceptibility, and frequent misidentification. CASE REPORT: This study reported a case of onychomycosis in a 46-year-old immunocompetent male caused by Chaetomium globosum. Diagnosis was established by direct potassium hydroxide microscopy of nail clippings, which revealed septate hyphae, and fungal culture that produced pigmented colonies with characteristic microscopic features. Antifungal susceptibility testing, performed according to CLSI M38 guidelines, showed sensitivity to itraconazole (MIC=0.25 µg/mL). The patient was treated with oral itraconazole and topical 5% nail lacquer (Nailrox, India), resulting in significant clinical improvement. CONCLUSION: This case highlighted the importance of accurate fungal identification, which is crucial in atypical nail infections, and occupational exposure should be considered in non-dermatophytic onychomycosis.