Patients with chronic granulomatous disease (CGD), a rare immune system disorder, are highly susceptible to serious fungal infections. This study of 99 patients over 28 years found that 40% developed fungal infections, mostly caused by Aspergillus fungi affecting the lungs. These infections were life-threatening, with over half the infected patients dying despite aggressive treatment with antifungal medications. Doctors need to screen for fungal infections early, even in patients without obvious symptoms, and treat infants and males more aggressively.