Bronchiolitis obliterans organizing pneumonia (BOOP) is a rare inflammatory lung disorder. Symptoms of BOOP include a flu-like illness in many individuals, cough and shortness of breath with exertional activities. Wheezing and hemoptysis are rare. The term bronchiolitis obliterans refers to swirls or plugs of fibrous, granulation tissue filling the small bronchiole airways. Organizing pneumonia refers to organized swirls of inflammatory tissue filling the small spherical units of the lungs referred to as alveoli and the alveolar ducts. Individuals with BOOP experience inflammation of the bronchioles and alveolar lung spherical units simultaneously, which distinguishes it from other similar inflammatory lung disorders.
Although several different known causes of BOOP have been identified, most cases occur for no known reason (idiopathic). Idiopathic BOOP may also be called cryptogenic organizing pneumonia. Some researchers prefer the use of COP to avoid confusion with other lung disorders with similar names. The term cryptogenic denotes that the cause of the disorder is unknown. Others prefer the term BOOP because it the most recognized term for the disorder, and others refer to it as Epler’s pneumonia.