Pulmonary complications of systemic vasculitides.

The pulmonary vasculitides are a heterogeneous group of diseases that often occur as a component of systemic vasculitic diseases. Most frequently, pulmonary vasculitis is observed in vasculitic syndromes that preferentially affect small vessels. Pulmonary involvement may develop because the lung has an extensive vascular and microvascular network. Sensitising antigens can easily reach the lung, and there are large numbers of vasoactive and activated immune cells in the lung. A diagnosis often can be made on the basis of clinical presentation and serologic studies, but biopsy of skin, nose, kidney, or lung may be necessary to ascertain the precise syndrome.