Vasculitis is defined generically as inflammation of a vessel. Hemorrhage is defined generically as the escape of blood from vessels. Were pulmonary vasculitis and pulmonary hemorrhage so directly connected that inflammation of blood vessels led to rupture and then hemorrhage, the classification of the vasculitic and hemorrhagic syndromes would be considerably easier. However, inflamed vessels may leak or not leak; inflammation in vessels may have great or little clinical or pathophysiological significance; and hemorrhage may be due to trauma, vascular anomalies, pulmonary hypertension, or a bleeding diathesis in the absence of inflammation or vascular necrosis.
There are many schemes for classifying vasculitis.
One can classify vasculitis by organ involvement, etiology, histology, size of blood vessel, immunological parameters, cellular mediation, or associated systemic disease. Various categorizations are given in Table 1.
In this chapter we separate the large and complex topic into three major groups: antineutrophil cytoplasmic antibody (ANCA)-associated diseases; pulmonary hemorrhage syndromes; and idiopathic vasculitides that rarely affect the lung. Many other entities, including but not limited to pulmonary infections, interstitial lung diseases such as sarcoidosis/necrotizing sarcoid granulomatosis and Langerhans cell histiocytosis, pulmonary hypertension, drugs, transplantation, radiation, systemic processes including connective tissue disease and inflammatory bowel disease, and malignancies, especially lymphoproliferative disorders such as lymphomatoid granulomatosis, cause pulmonary vasculitis and/or hemorrhage. These entities are discussed elsewhere in this text.