Idiopathic pulmonary fibrosis (cryptogenic fibrosing alveolitis) is the most common form of idiopathic interstitial pneumonia (see Overview of Idiopathic Interstitial Pneumonias).
In idiopathic pulmonary fibrosis, the lungs develop progressive scarring for unknown reasons. . It is thought that aging causes the lungs' response to normal stresses to become abnormal and harmful, causing scarring.
Symptoms depend on the extent of the lung damage, the rate at which the disease progresses, and whether complications, such as lung infections and right-sided heart failure (cor pulmonale—see Sidebar 1: Cor Pulmonale: A Disorder Stemming From Pulmonary Hypertension) develop. The main symptoms start insidiously as shortness of breath during exertion, cough, and diminished stamina. In most people, symptoms worsen over a period ranging from about 6 months to several years.
As the disease progresses, the level of oxygen in the blood decreases, and the skin may take on a bluish tinge (called cyanosis) and the ends of the fingers may become thick or club-shaped (see Fig. 1: Recognizing Finger Clubbing). Strain on the heart may cause the right ventricle to enlarge, eventually resulting in right-sided heart failure. Through a stethoscope, doctors often hear crackling sounds in the lungs.
A chest x-ray may show lung damage, most plentiful in the lower parts of both lungs. Computed tomography (CT) typically shows the damage and thick scarring in more detail. Pulmonary function tests (see Pulmonary Function Testing (PFT)) show that the amount of air the lungs can hold is below normal. Analysis of a blood sample or use of an oximeter (see Arterial Blood Gas (ABG) Analysis) shows a low level of oxygen with minimal exercise (walking at a normal pace) and, as the disease progresses, even when the person is resting.
To confirm the diagnosis, doctors may do a lung biopsy by using a procedure called bronchoscopy (see Bronchoscopy). Many times, a larger tissue sample is needed and must be removed surgically, sometimes with use of a thoracoscope (see Thoracoscopy).
Blood tests cannot confirm the diagnosis but are done as part of the search for other disorders that may cause a similar pattern of inflammation and scarring. For example, doctors do blood tests to screen for certain autoimmune disorders.
Prognosis and Treatment
Most people continue to get worse. On average, people live about 3 years after diagnosis. Some people survive for more than 5 years after diagnosis. A few die within several months.
Pirfenidone, available in some countries, appears to slow lung scarring. Other treatments are being studied.
Other treatments are aimed at relieving symptoms: pulmonary rehabilitation for improving ability to carry out activities of daily life (see Overview of Pulmonary Rehabilitation), oxygen therapy for low blood oxygen levels, antibiotics for infection, and drugs for the heart failure that is caused by cor pulmonale. Lung transplantation (in some cases with a single lung) has been successful in some people with severe idiopathic pulmonary fibrosis.
Last full review/revision October 2013 by Harold R. Collard, MD