A 55-year-old woman developed a rare fungal infection called Aspergillus bronchitis in a mucus plug within her lung over a 9-year period. Although she was otherwise healthy with a normal immune system, the fungus gradually grew and eventually caused serious bleeding in her lungs. Doctors treated the bleeding with artery embolization and then surgically removed the affected lung tissue. The fungus was identified as Aspergillus udagawae, a type that is harder to treat with standard antifungal medications.