Diffuse Alveolar Hemorrhage
Understand the principles of classification of vasculitis.
Describe the spectrum of pulmonary vasculitides and their clinical manifestations.
Describe the principles of treatment for the antineutrophil cytoplasmic autoantibodies (ANCA)-associated vasculitis syndromes.
Describe the differential diagnostic approach to the patient presenting with diffuse alveolar hemorrhage.
Review specific diseases that can cause diffuse alveolar hemorrhage.
Pulmonary vasculitis, defined as inflammation of the pulmonary vessels, is usually but one manifestation of a systemic vasculitis. The vasculitis syndromes are separated into primary (unknown etiology) and secondary (known etiology or related to another defined syndrome such as a collagen vascular disease) vasculitides. The systemic vasculitides are further classified by the size of vessels predominantly affected: large-vessel, medium-sized-vessel, and small-vessel vasculitides. The small-vessel vasculitides are further divided into those that are associated with immune-complex deposits versus those that are not (pauci-immune). The pauci-immune small-vessel vasculitides are usually associated with antineutrophil cytoplasmic autoantibodies (ANCA), and consequently also called ANCA-associated vasculitides. The ANCA-associated vasculitides, granulomatosis with polyangiitis (Wegener), microscopic polyangiitis (MPA), and eosinophilic granulomatosis with polyangiitis (EGPA) (Churg-Strauss) most commonly affect the respiratory tract. The spectrum of their clinical presentations and their management is described in detail. Not all respiratory manifestations in patients with vasculitis are caused by the vasculitis. Diffuse alveolar hemorrhage (DAH) results from the disruption of the alveolar-capillary basement membrane. This can be caused by immune-mediated systemic disease processes that cause capillaritis, by the direct toxic effects of inhaled or blood-borne agents, by coagulopathies, or by mitral valve disease. The small-vessel vasculitides, granulomatosis with polyangiitis (Wegener), and MPA are the vasculitis syndromes that most commonly lead to capillaritis with DAH, but many other systemic autoimmune disorders can also cause capillaritis. A systematic diagnostic approach to the patient with DAH is described.