Successful treatment with rezafungin after micafungin for relapsing Rasamsonia argillacea species complex pneumonia in a patient with bronchiectasis: A case report

Rasamsonia argillacea species complex are emerging opportunistic molds increasingly reported in patients with chronic lung disease. We describe a 69-year-old woman with bronchiectasis who developed relapsing R. aegroticola pneumonia. After transient improvement with micafungin, relapse occurred, and antifungal therapy was switched to rezafungin, a novel echinocandin with a prolonged half-life and front-loaded pharmacokinetics. A total of 3 months of treatment led to clinical and radiological improvement, with sustained stability 6 months after therapy completion. This case illustrates the pathogenic role of R. argillacea species complex in non-immunocompromised hosts and suggests rezafungin as a promising therapeutic option for echinocandin-susceptible, azole-resistant Rasamsonia infections.