Rob Neville of Savara Pharmaceuticals discusses Pulmonary Alveolar Proteinosis (PAP) is a rare lung disease, which affects approximately 7 persons in a million people. It is characterised by the build-up of grainy material in the air sacs (alveoli) in the lungs. The grainy material consists of proteins and lipids from lung surfactant – an important substance that coats the inside of the air sacs to prevent the lungs from collapsing.
The air sacs need to be inflated for the lungs to absorb the oxygen that the patient breathes and transfer it to the blood circulation. The body continuously produces new active surfactant. In healthy lungs the old, inactivated surfactant is digested by immune cells called alveolar macrophages. They are the dustmen or garbage collectors of the body and they have a very important task of keeping the alveoli clean. In PAP lungs, however, the macrophages fail to clean the air sacs. Consequently, the old surfactant material builds up gradually in the lungs and eventually fills the alveoli causing the patient to feel breathless. Scientific research shows that the macrophages need to be stimulated by the GM-CSF protein in order to function. In PAP lungs, however, the GM-CSF protein is either inactivated or defective, rendering the macrophages or dustmen unable to perform their cleaning tasks. The patient is commonly a man in early middle age who experiences increasing breathing difficulty, first with exertion, later at rest while developing a cough.
There may be episodes of fever, chest pain, or coughing blood, especially if secondary lung infection develops. The best available treatment today is periodic whole lung lavage (WLL), i.e. washing out the lungs under general anesthesia. This requires admission to intensive care, which is an invasive and inconvenient procedure that can only be conducted effectively and safely by highly experienced physicians at a few specialist sites.