New perspectives in pulmonary angiitis. From pulmonary angiitis and granulomatosis to ANCA associated vasculitis

Traditionally clinical and histopathological features were mainly relied on for classification of vasculitis and granulomatosis of the lung. These can be complemented by immunodiagnostic features which contribute to the classification as well as to the understanding of the pathogenesis of these disorders. Previously five conditions were classified together under the heading 'pulmonary angiitis and granulomatosis' (PA and G), mainly on the basis of histological similarities. These conditions have in common a granulomatous histopathology together with necrosis of varying degree, pulmonary vasculitis and occasionally systemic vasculitis. The introduction of novel immunodiagnostic methods led to different approaches of classification, specifically a separation between a group of disorders associated with antinuclear antibodies (ANA), referred to as collagen vascular diseases, and a group of systemic autoimmune diseases unrelated to ANA, referred to as primary systemic vasculitides. Among the latter, Wegener's granulomatosis (WG), Churg-Strauss syndrome (CSS) and microscopic polyangiitis (MPA) are associated with a group of autoantibodies (antineutrophil cytoplasmic antibodies-ANCA) which separate them from other members of the PA and G group. The granulomatous and vasculitic disorders WG and CSS together with the non-granulomatous small-vessel vasculitis MPA now form a new group of diseases ('ANCA-associated vasculitides') which have many clinical, serological and immunohistochemical features in common. Collagen vascular diseases (CVD) are serologically characterized by distinct subspecificities of antinuclear antibodies (ANA), sometimes pronounced hypergammaglobulinaemia, complement consumption and immune deposits (antigen-antibody-complement complexes) which are common in situ in immune-complex vasculitis. In this article newer aspects of the clinical course, the immunodiagnostic procedure, and the immunopathogenesis of the relatively large group of pulmonary angiitis will be described.