Pulmonary fibrosis is the thickening and scarring of the lungs which impedes breathing. This makes it difficult for oxygen to pass from the lungs into the blood stream. It can be caused by variety of factors including airborne toxins, diseases, and even some medical treatments. Most of the time the cause of this scarring is unknown, which is referred to as idiopathic pulmonary fibrosis. Symptoms include shortness of breath, dry cough, fatigue, unexplained weight loss, and aching joints and muscles. Risk factors for pulmonary fibrosis include age, occupation, smoking, cancer treatments, and genetic factors. Complications that occur as a result of pulmonary fibrosis include pulmonary hypertension, right-sided heart failure, respiratory failure, and lung cancer. Although idiopathic pulmonary fibrosis usually only occurs in one person in a family, a small percentage of people with this disease have a least one other affected family member. When idiopathic pulmonary fibrosis occurs in more than one family member, it is referred to as familial pulmonary fibrosis.