Pulmonary vasculitis.

Pulmonary vasculitis encompasses inflammation in the pulmonary vasculature with involved vessels varying in caliber from large elastic arteries to capillaries. Small pulmonary capillaries are the vessels most commonly involved in vasculitis affecting the lung. The antineutrophil cytoplasmic antibody-associated vasculitides, which include granulomatosis with polyangiitis (formerly Wegener granulomatosis), microscopic polyangiitis, and eosinophilic granulomatosis with polyangiitis (formerly Churg-Strauss syndrome), are the small vessel vasculitides in which pulmonary vasculitis is most frequently observed and are the major focus of this review. Vasculitic involvement of the large pulmonary vessels as may occur in Behçet syndrome and Takayasu arteritis is also discussed.