The classification of pulmonary vasculitides into specific categories is often difficult because of the lack of precise criteria. Because of this difficulty, consensus guidelines have been developed in order to gather data and to develop treatment strategies. At the Chapel Hill Consensus Conference, MPA was defined as necrotizing vasculitis of small vessels (ie, capillaries, venules, or arterioles), with few or no immune deposits, while a necrotizing arteritis that involves medium-sized arteries may also be observed.5 In MPA, necrotizing glomerulonephritis is a very common clinical presentation, while pulmonary capillaritis resulting in alveolar hemorrhage occurs frequently.7 MPA is generally associated with ANCA. Patients may have p-ANCA with antimyeloperoxidase specificity or, more rarely, c-ANCA with antiproteinase-3 specificity. Cutaneous, musculoskeletal, GI, neurologic, and ear, nose, and throat organ system involvement may also be found, but occur less frequently than renal involvement, the latter of which is reported in 90% of cases.