Pulmonary Fibrosis involves the overgrowth, hardening, and/or scarring of lung tissue due to excess collagen. The most common variation of this disease is Idiopathic Pulmonary Fibrosis, which is lung fibrosis from unknown causes. Common symptoms include shortness of breath, a chronic dry cough, fatigue, weakness, chest discomfort, loss of appetite, and rapid weight loss. It usually affects people between the ages of 40 and 70, and men and women are equally affected. The prognosis for patients with this disease is poor, and are usually only expected to live an average of 4 to 6 years after diagnosis.