Pulmonary sarcoidosis occurs when small patches of inflamed cells appear on the lungs' airsacs, breathing tubes or lymph nodes. This causes the lungs to become stiff and unable to hold as much air as healthy lungs, according to the American Lung Association.
Pulmonary sarcoidosis is a type of autoimmune disease with an unknown cause. How it spreads to other parts of the body is still under study. However, pulmonary sarcoidosis heals on its own without medical treatment in half of all cases, according to the American Lung Association. For severe cases, a doctor can treat the symptoms to improve lung function, as stated by WebMD.com.