Abstract
Defined by the accumulation of red blood cells into the alveolar space, diffuse alveolar
hemorrhage (DAH) is a severe and potentially fatal medical condition requiring careful
attention. In contrast to simple extravasation of erythrocytes facilitated by impaired
hemostasis or hemodynamic causes, DAH in vasculitis is due to capillaritis, that is,
inflammation of capillaries. Dyspnea, hemoptysis, chest infiltrates, and abrupt fall
of blood hemoglobin level represent the cardinal features of DAH; yet, hemoptysis
is lacking in one-third of cases. Bronchoalveolar lavage, retrieving bright red fluid,
is the best diagnostic clue, also excluding infection and other causes of hemoptysis.
Although not recommended, lung biopsy is the gold standard for the diagnosis of DAH
and pulmonary capillaritis. Pulmonary capillaritis may be primary as in antineutrophil
cytoplasmic antibody (ANCA)-associated vasculitis or secondary to drugs (especially
antithyroid drugs such as propylthiouracil), infections, connective tissue diseases
especially systemic lupus erythematosus, or other small vessel vasculitides. Newer
toxic causes of drugs of abuse may be difficult to diagnose. Granulomatosis with polyangiitis
and microscopic polyangiitis are the most common causes of capillaritis and DAH, whereas
DAH is extremely rare in eosinophilic granulomatosis with polyangiitis. When pulmonary
capillaritis is not secondary to underlying systemic vasculitis, idiopathic pauci-immune
pulmonary capillaritis may be considered, with or without ANCA. Supportive treatment
strategy is mandatory in all cases of DAH. Mechanical ventilation and extracorporeal
membrane oxygenation may be used in severe cases. Early identification and removal
of the putative drug is crucial in drug-induced vasculitis/DAH and may obviate the
need for immunosuppressive therapy. High-dose corticosteroids, intravenous cyclophosphamide,
and recently rituximab are the mainstay of treatment in vasculitis. Plasma exchange
is recommended in anti–glomerular basement membrane disease and in severe DAH associated
with systemic lupus erythematosus and is used in selected cases in ANCA-associated
vasculitis.
Keywords
diffuse alveolar hemorrhage - pulmonary vasculitis - connective tissue disease - ANCA-associated
vasculitis - respiratory failure - rituximab
