Pulmonary alveolar proteinosis (PAP) is a rare disease characterised by the accumulation of protein-rich liquid in the alveoli. Even though its pathogenesis is unknown, it is suggested that the accumulation of phospholipids-rich proteinaceous material, positively painted with periodic acid-Schiff (PAS), in the alveoli results from degeneration of the maturation or functions of alveolar macrophages and defects in the functions of granulocyte-macrophage-colony stimulating factor (GM-CSF). Primary PAP is frequently seen in young males without preceding diseases.1
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