Pulmonary fibrosis is a condition leading to a build-up of scar tissue in the lungs. Over time, the lungs lose their ability to take in and transfer oxygen into the bloodstream. This leads to symptoms that significantly affect a person’s ability to perform daily activities and can even be life-threatening. Pulmonary fibrosis can be progressive and is a disorder affecting the connective tissue in-between the lungs. Pulmonary fibrosis belongs to a group of so-called interstitial lung diseases.