Pulmonary alveolar proteinosis (abbreviated
PAP), is a rare
lung disease in which abnormal accumulation of
pulmonary surfactant occurs within the
alveoli, interfering with
gas exchange. PAP can occur in a primary form or secondarily in the settings of malignancy (especially in myeloid
leukemia), pulmonary infection, or environmental exposure to dusts or chemicals. Rare familial forms have also been recognized, suggesting a
genetic component in some cases.