The significance of antineutrophil cytoplasmic antibody in microscopic polyangitis and classic polyarteritis nodosa.

AIMS To describe the distribution and features of classic polyarteritis nodosa (PAN) and microscopic polyarteritis (MPA) and the importance of antineutrophil cytoplasmic antibody (ANCA) in childhood PAN. METHODS Classic PAN was diagnosed in 15 patients based on the presence of aneurysms on angiography in 10 patients and of necrotising vasculitis in medium sized arteries in five. MPA was diagnosed in 10 patients, based on characteristic findings at renal biopsy in six and by the presence of small sized necrotising arteritis in four. Serum ANCA was detected initially by indirect immunofluorescence (IIF) followed by an immunoassay for myeloperoxidase (MPO) in each case. RESULTS The median age of the patients with classic PAN and MPA was 12 (range 8-17) and 9.5 (range 5-14) respectively. None of the patients with classic PAN had renal failure. Six of the patients with MPA presented with renal failure; four progressed to chronic renal failure. Clinically evident pulmonary-renal syndrome was present in three of the 10 patients with MPA. IIF for ANCA in classic PAN was negative in nine, showed mild staining patterns in six, and in one MPO-ELISA was mildly increased. IIF for ANCA in MPA revealed very strong perinuclear ANCA staining in nine and atypical staining in one. In MPA, median MPO-ELISA level was 42.5 EU/ml (range 20-250). Treatment of childhood PAN was satisfactory with effective treatment; however relapses did occur. CONCLUSION ANCA is useful in the diagnosis and follow up of MPA.