A 5-year-old girl with systemic juvenile arthritis being treated with immunosuppressive medications developed a rare and serious fungal infection in her nose and sinuses caused by a mold called Lichtheimia. The infection caused tissue death and spread toward her brain, but was successfully treated with combination antifungal drugs and surgery. This case highlights how powerful immunosuppressive treatments for severe arthritis can increase the risk of life-threatening fungal infections.