Pulmonary alveolar proteinosis (PAP) is a rare lung disorder characterized by the filling of the pulmonary alveoli with proteinaceous material. This material consists of surfactant phospholipids and apoproteins and stains positive with periodic acid-Schiff (PAS) stain. Alveolar architecture is typically preserved, and inflammatory cell infiltration is minimal.
There are 3 categories of the condition:
Autoimmune and hereditary PAP – Causes disruption of granulocyte-macrophage colony-stimulating factor (GM-CSF).
Congenital PAP – Genetic disorder of surfactant production; presents in neonates.
Secondary PAP – Associated with mineral dust exposure, hematologic malignancies, and allogenic hematopoietic cell transplantation.
Typical age of presentation in adults with PAP is between 40 and 50 years. Smoking is a significant risk factor. Some patients will have other autoimmune diseases.
Signs and symptoms include dyspnea, particularly on exertion, cough, and low-grade fever. The classic radiographic pattern is "crazy paving" on high-resolution CT, but other patterns may be observed.
Neonates with congenital PAP present in the first 1-2 years of life with symptoms ranging from severe respiratory failure in the neonatal period to insidious chronic interstitial lung disease in later months.
