Pulmonary fibrosis harms the tissues deep in your lungs. The air sacs in your lungs and their supporting structures become scarred and make your lungs thick and stiff. That makes it hard to breath, and your blood may not get enough oxygen.
One cause of pulmonary fibrosis is interstitial lung disease, named for a large group of diseases that inflame or scar the lungs. Pulmonary fibrosis is also associated with some connective tissue diseases. It can be a side effect of a medicine, but we are unsure about the actual cause of the disease. Smoking can boost your risk or make the illness worse.