Bronchiolitis obliterans is sometimes confused in the public mind with bronchiolitis obliterans organizing pneumonia (BOOP), a completely different pulmonary disorder. Bronchiolitis obliterans is a rare and life-threatening form of fixed obstructive lung disease in which the bronchioles are plugged with granulation tissue. It is a common sequela of bone marrow, lung, and heart-lung transplantation, but can also occur as a complication of certain pulmonary infections, adverse drug reaction, toxic inhalation, and autoimmune disorders. Bronchiolitis obliterans may develop in the allograft lung through several means. In the usual proposed sequence the bronchioles of the lung have their submucosa infiltrated by a mononuclear cell population, primarily small round, small cleaved, and occasional large lymphoid cells. |