Pulmonary alveolar proteinosis
Pulmonary alveolar proteinosis (PAP) is a rare lung disorder characterized by an abnormal accumulation of surfactant-derived lipoprotein compounds within the alveoli of the lung. The accumulated substances interfere with the normal gas exchange and expansion of the lungs, ultimately leading to difficulty breathing and a predisposition to developing lung infections.
Source: Wikipedia — Pulmonary alveolar proteinosis (CC BY-SA 4.0)