The Nongranulomatous Vasculitides of the Lung

Abstract

This paper describes the unique interstitial lung lesion of pulmonary capillaritis, which is a true small vessel vasculitis of the lung, first described in 1957. This consists of a disruption of the alveolar interstitium due to an infiltration of neutrophils. Because of the neutrophilic infiltration and their subsequent fragmentation (necrosis), fibrinoid necrosis of the alveolar septal results and red blood cells and fibrin leak through a damaged alveolar capillary basement membrane into the alveolar spaces, resulting in diffuse alveolar hemorrhage. Most etiologies of pulmonary capillaritis are associated with either a systemic vasculitis such as Wegener's granulomatosis and microscopic polyangiitis or collagen vascular disease, particularly systemic lupus erythematosus. Most instances of pulmonary capillaritis occur in the presence of serum antineutrophilic cytoplasmic antibodies, but this is not the case for all causes of this lesion. The presence of these antibodies in the sera of patients with the clinical syndrome of diffuse alveolar hemorrhage indicates underlying pulmonary capillaritis. There are also cases of pulmonary capillaritis and diffuse alveolar hemorrhage that are confined to the lung and are not associated with serological or clinical evidence of a systemic disease. These have been termed isolated pulmonary capillaritis. It is likely that cases of isolated pulmonary capillaritis in adults were previously considered to be idiopathic pulmonary hemosiderosis. The recommended treatment for the capillaritis lesion is corticosteroids in addition to immunosuppressive therapy. For some etiologies, particularly Goodpasture's syndrome, plasmaphoresis is considered to be efficacious.