A 65-year-old woman who received a lung transplant developed a serious brain infection caused by a rare fungus called Rasamsonia argillacea. Doctors initially struggled to identify this unusual fungus and treated her with multiple antifungal medications, but the infection proved difficult to control because the fungus was resistant to common antifungal drugs. Investigations revealed that the patient had an undiagnosed immune system disorder called chronic granulomatous disease, which made her vulnerable to this rare infection. Despite aggressive treatment including surgery and powerful antifungal medications, the patient’s condition worsened and she eventually passed away.