[Histopathology of systemic vasculitis]

Inflammatory diseases of blood vessels can occur in any part of the vascular system with a variety of clinical and histopathological manifestations. Possible etiologies include primary systemic vasculitis, secondary vasculitis or isolated single organ vasculitis. Key criteria of morphological vasculitis work-up are vessel size, type of inflammation (granulomatous, necrotizing and/or leukocytoclastic) as well as presence or absence of immune complexes and extravascular inflammatory changes. Together with the typical organ involvement and serological data, these criteria constitute the basis of vasculitis classification. A histopathologically confirmed biopsy is the gold standard for a diagnosis of vasculitis, although a definite diagnosis can frequently not be made solely on histopathological grounds. Differential diagnostic overlaps and possible ways of discrimination are presented. In many cases, however, histopathology can only provide a definite diagnosis in combination with clinical and serological data. A conclusive morphological diagnosis depends on the right time of biopsy and selection of appropriate biopsy material.