The word “pulmonary” means lung and the word “fibrosis” means scar tissue— similar to scars that you may have on your skin from an old injury or surgery. So, in its simplest sense, pulmonary fibrosis (PF) means scarring in the lungs. Over time, the scar tissue can destroy the normal lung and make it hard for oxygen to get into your blood. Low oxygen levels (and the stiff scar tissue itself) can cause you to feel short of breath, particularly when walking and exercising. Pulmonary fibrosis isn’t just one disease. It is a family of more than 200 different lung diseases that all look very much alike. The PF family of lung diseases falls into an even larger group of diseases called the interstitial lung diseases (also known as ILD), which includes all of the diseases that have inflammation and/or scarring in the lung. Some interstitial lung diseases don’t include scar tissue. When an interstitial lung disease does include scar tissue in the lung, we call it pulmonary fibrosis.