A rare fungal threat: Successful management of pan-drug resistant Microascus cirrosus peritonitis in a PD patient.

Microascus cirrosus is a rare environmental mold not previously genetically confirmed as a cause of peritoneal dialysis (PD)-associated peritonitis. We report the first culture- and multilocus sequencing-verified case in an immunocompetent PD patient who fulfilled ISPD diagnostic criteria, presenting with cloudy effluent and neutrophilic inflammation despite minimal systemic symptoms. Early clues included black intraluminal catheter debris and a positive galactomannan index in peritoneal dialysate. Definitive identification required ITS, LSU, SSU, and β-tubulin sequencing after initial morphologic misclassification. The isolate demonstrated elevated antifungal MICs without established clinical breakpoints. Clinical stabilization followed prompt catheter removal with adjunctive therapy. This case highlights the pathogenic potential of environmental molds in PD and underscores the primacy of molecular diagnosis and early source control in device-associated fungal peritonitis.