The first case of isolation of Magnusiomyces capitatus from the oral cavity of an addicted patient.

Magnusiomyces capitatus (M. capitatus) is an emerging opportunistic yeast, rarely found as a causal agent of invasive fungal infection. In this study, we report a 31-year-old man infected with M. capitatus in the oral cavity, with a history of heroin and amphetamine abuse. M. capitatus was isolated through culture and microscopic analysis and identified by PCR amplification of the ITS DNA region. Based on the in vitro antifungal susceptibility test, the lowest MICs for M. capitatus were recorded for nystatin, itraconazole, and amphotericin, while higher MICs were observed for caspofungin and fluconazole. Treatment with nystatin successfully eliminated M. capitatus and relieved the clinical symptoms. This study presents the first case of M. capitatus in a patient with substance use disorder, manifesting as a plaque-like ulcer in the oral cavity.