[Histomorphology of interstitial lung disease and pulmonary vasculitis]

Rheumatic diseases or collagen vascular diseases represent a heterogeneous group of immunologically mediated inflammatory disorders. The respiratory system is often affected,the causes being manifold: infection, medication toxicity and specific manifestations of immunological processes due to the underlying disease. The lung can be involved in all its components. Due to their extremely broad differential diagnosis, pulmonary vasculitic syndromes still constitute a major challenge for the pathologist. Pulmonary involvement is frequent in primary systemic vasculitis (PSV) associated with anti-neutrophil-cytoplasmic antibodies (ANCA); other PSV only rarely affect the lungs. Histomorphologically, small vessel vasculitis with neutrophil alveolitis and diffuse alveolar hemorrhage, as well as extravascular intraparenchymal or peribronchial granulomas, can point to PSV. A single biopsy is often insufficient to identify all diagnostic criteria. Therefore, the selection of suitable biopsy material and correlation with clinical, serological and radiological parameters is indispensable. Almost all forms of interstitial lung disease may be present in collagen vascular disease; however, several parallel morphological types, rather than one in isolation, are frequently found.