BOOP has no known cause. However, other forms of bronchiolitis obliterans and organizing pneumonia may be associated with specific diseases or situations, such as bone marrow, heart, or heart-lung transplantation; collagen vascular diseases, such as rheumatoid arthritis or systemic lupus erythematosus; inflammatory diseases, such as Crohn’s disease, ulcerative colitis, or polyarteritis nodosa; bacterial, viral, or mycoplasmal respiratory tract infections; inhalation of toxic gases; or drug therapy with amiodarone, bleomycin, penicillamine, or lomustine.

The presenting symptoms of BOOP are usually subacute, with a flulike syndrome of fever, persistent and nonproductive cough, dyspnea (especially on exertion), malaise, anorexia, and weight loss lasting from several weeks to several months. Physical assessment findings may reveal dry crackles as the only abnormality. Less common signs and symptoms include a productive cough, hemoptysis, chest pain, generalized aching, and night sweats.

Diagnosis begins with a thorough patient history meant to exclude any known cause of bronchiolitis obliterans or diseases with a pathology that includes an organizing pneumonia pattern.