Antineutrophil cytoplasmic antibodies (ANCA) and small vessel vasculitis.

We report on one patient with Wegener's granulomatosis (WG) and two patients with microscopic polyangiitis (MPA). The patient with WG had signs of a respiratory infection and showed a c-ANCA pattern with proteinase 3 (PR3) specificity. The patients with MPA presented with pulmonary haemorrhage and signs of renal damage and showed a p-ANCA pattern with myeloperoxidase (MPO) specificity. In the three patients histopathological findings confirmed the diagnosis. We discuss the clinical indications of ANCA testing and the current terminology for reporting ANCA results (c-ANCA, p-ANCA, c-ANCA (atypical) and atypical ANCA). The target antigens and diseases associated with these different patterns are considered. Finally we focus on the value of ANCA and more specific PR3-ANCA and MPO-ANCA in the diagnosis of WG and MPA. The new application domain of ANCA in Crohn's disease and ulcerative colitis is also discussed.