[Diffuse alveolar hemorrhage].

Diffuse alveolar hemorrhage is a clinical syndrome that can be life threatening if not diagnosed and treated in time. In most cases it occurs largely as a result of small-vessel vasculitis of the lungs. The many different forms can be classified into 3 large groups: a) pauciimmune disease, which generally involves pulmonary capillaritis and is associated with the presence of antineutrophil cytoplasmic antibodies; b) syndromes caused by immune deposits, which can be detected by immunofluorescence; and c) a large miscellaneous group that includes drug reactions, infections, and idiopathic disease. Diagnosis is based on a combination of signs, symptoms, serology, and histology. Biopsy with video-assisted thoracoscopy should be recommended in patients with diffuse alveolar hemorrhage without known cause and with no prior diagnosis of systemic disease, in whom serology studies do not reveal conclusive data, and in general in those patients for whom there is a high level of suspicion of diffuse alveolar hemorrhage. In all such cases, the fresh biopsy material should be sent to the pathology laboratory for preparation of frozen sections to be used for immunofluorescence.