Alveolar hemorrhage (AH) is an important pulmonary manifestation of small vessel vasculitis because severe presentations are the most common vasculitic cause of early death. Renal vasculitis is usually present with AH; the combination is known as pulmonary-renal syndrome. Early diagnosis and intensive therapy are of particular importance to reduce early mortality and improve longer-term outcomes. The commonest immune-mediated cause of AH is anti-neutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV) (80%), with other vasculitides, including systemic lupus erythematosus and anti-glomerular basement membrane disease accounting for 20%. One quarter of AAV patients develop AH, which when mild is associated with a good outcome, but mortality rises to 50% for cases with respiratory failure requiring ventilator support. The prognosis of AH in the other vasculitides is generally favorable, but cases are rare and experience is limited. Treatment follows similar regimens to those for other AAV presentations, although when severe there is widespread use of parenteral glucocorticoids together with plasma exchange. These interventions have developed empirically supported by a theoretical rationale but have not been validated by randomized clinical trials. Sepsis and cardiovascular and thromboembolic events are important early complications. and long-term follow-up is required to monitor for and prevent relapse and manage disease-related damage. A minority of cases develop on a background of pulmonary fibrosis, or progressive pulmonary fibrosis develops after vasculitis has gone into remission.
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