Autoimmune Pulmonary Alveolar Proteinosis in a Patient With Chronic Disseminated Blastomycosis: A Case Report.

Pulmonary alveolar proteinosis (PAP) is a rare diffuse lung disease characterized by the intra-alveolar accumulation of surfactant, leading to progressive gas exchange impairment. While autoimmune PAP, driven by granulocyte-macrophage colony-stimulating factor (GM-CSF) autoantibodies, accounts for the majority of cases, its association with chronic fungal infections is exceedingly rare. Only one prior case of PAP occurring in the setting of active blastomycosis has been documented since 1995. We present a unique case of a patient with chronic disseminated blastomycosis who developed worsening respiratory failure due to the development of autoimmune PAP. It highlights the importance of broadening the differential diagnosis when patients with known pulmonary infections fail to respond to appropriate antimicrobial therapy.