Bronchiolitis obliterans organizing pneumonia (BOOP) is a lung disease that causes inflammation in the small air tubes (bronchioles) and air sacs (alveoli). BOOP typically develops in individuals between 40-60 years old; however the disorder may affect individuals of any age. The signs and symptoms of BOOP vary but often include shortness of breath, a dry cough, and fever. BOOP can be caused by viral infections, various drugs, and other medical conditions. If the cause is known, the condition is called secondary BOOP. In many cases, the underlying cause of BOOP is unknown. These cases are called idiopathic BOOP or cryptogenic organizing pneumonia. Treatment often includes corticosteroid medications.

Signs and symptoms of BOOP vary. Some individuals with BOOP may have no apparent symptoms, while others may have severe respiratory distress as in acute, rapidly-progressive BOOP. The most common signs and symptoms of BOOP include shortness of breath (dyspnea), dry cough, and fever. Some people with BOOP develope a flu-like illness with cough, fever, fatigue, and weight loss.

BOOP may be caused by a variety of factors, including viral infections, inhalation of toxic gases, drugs, connective tissue disorders, radiation therapy, cocaine, inflammatory bowl disease, and HIV infection. In many cases, the underlying cause of BOOP is unknown. These cases are called idiopathic BOOP or cryptogenic organizing pneumonia (COP).

BOOP is typically diagnosed by lung biopsy, although imaging tests and pulmonary function tests can also provide information for diagnosis.

Other medications reported in the medical literature to be beneficial for individuals on a case-by-case basis include: cyclophosphamide, erythromycin in the form of azithromycin, and Mycophenolate Mofetil (CellCept). More research is needed to determine the long-term safety and effectiveness of these potential treatment options for individuals with BOOP.

In rare cases, lung transplantation may be necessary for individuals with BOOP who do not respond to standard treatment options.