Pulmonary fibrosis is the formation or development of excess fibrous connective tissue in the lungs. Symptoms of pulmonary fibrosis involve shortness of breath, chronic coughing, fatigue and weakness, and chest discomfort. The pathologic substrate is usual interstitial pneumonia. Pulmonary fibrosis can be idiopathic and then mostly is a disease in the 6th decade or older. Lung fibrosis is often associated with systemic diseases. Some occupational
pollutants (asbestos, gasses) are well-known for their fibrosis-enhancing properties. Smoking and certain drugs (e.g. amiodarone, bleomycin, methotrexate, and nitrofurantoin) can increase the risk or worsen the disease.
Lung fibrosis is a disease with poor response to therapy and an unfavourable outcome, most patients surviving only one or a few years.