Pulmonary vasculitis and pulmonary hemorrhage

Inflammation of arteries and veins in the lung can occur in a variety of inflammatory lung diseases. By convention, the term vasculitis is generally restricted to disorders in which vascular inflammation is a major driver of the pathologic process, which is usually immune-mediated. Pulmonary vasculitis and/or capillaritis and diffuse alveolar hemorrhage most commonly occur in the setting of three systemic vasculitic disorders including granulomatosis with polyangiitis (formerly Wegener granulomatosis), eosinophilic granulomatosis with polyangiitis (formerly Churg-Strauss syndrome), and microscopic polyangiitis. Occasionally, other vasculitic syndromes and systemic connective tissue diseases can involve the lung, including necrotizing sarcoid granulomatosis, giant cell (temporal) arteritis, polyarteritis nodosa, systemic lupus erythematosus, Takayasu arteritis, Goodpasture syndrome (anti-glomerular basement membrane disease), Henoch-Schönlein purpura (IgA vasculitis), and Behçet syndrome, among other miscellaneous and idiopathic conditions. Secondary vasculitis can also occur with pulmonary infections, septic emboli, and classic sarcoidosis. Evaluation of the patient with pulmonary hemorrhage can be a challenge for clinicians, radiologists, and pathologists. In this chapter, the histologic patterns of pulmonary vasculitis and diffuse alveolar hemorrhage are reviewed. A conceptual view of pulmonary hemorrhage is presented for the pathologist from a clinical standpoint, and a morphologic approach to the diagnosis of pulmonary hemorrhage is discussed. Specific disorders associated with vasculitis/capillaritis and diffuse alveolar hemorrhage are reviewed in detail, with clinical features, imaging findings, pathologic findings, and treatments discussed along with important differential diagnostic considerations.