Diffuse alveolar hemorrhage: diagnosing it and finding the cause.

Diffuse alveolar hemorrhage is an acute, life-threatening event, and repeated episodes can lead to organizing pneumonia, collagen deposition in small airways, and, ultimately, fibrosis. Among the many conditions it can accompany are Wegener granulomatosis, microscopic polyangiitis, Goodpasture syndrome, connective tissue disorders, antiphospholipid antibody syndrome, infectious or toxic exposures, and neoplastic conditions. Its many causes and presentations pose an important challenge to the clinician.