Circulating myeloperoxidase and anti-myeloperoxidase antibody in patients with vasculitis

To evaluate a role of myeloperoxidase (MPO) and antibody to myeloperoxidase (anti-MPO) in vasculitis. MPO and anti-MPO were determined by enzyme-linke d immunosorbent assays in sera From 43 patients with vasculitis, 40 with rh eumatoid arthritis, 36 with systemic lupus erythematosus (SLE), 23 with mix ed connective tissue disease, 13 with systemic sclerosis, 22 with polymyosi tis/dermatomyositis, 18 with Sjogren's syndrome, and 30 normal controls. Ki dney and lung sections from patients with vasculitis were stained for MPO. Anti-MPO titers were significantly higher (p < 0.005) in the patients with vasculitis (mean +/- SD absorbance at 405 nm: 0.53 +/- 0.37) than in any ot her groups (0.15 +/- 0.04 similar to 0.2 +/- 0.11). MPO levels in patients with vasculitis were comparable with those in patients with other diseases except SLE. In two patients with vasculitis, anti-MPO decreased sharply wit h simultaneous increases in MPO 1 - 2 weeks after they developed pulmonary hemorrhage. Numerous cells positive for MPO infiltrated the Box man's space s. These results indicate that MPO may contribute to the pathogenesis of va sculitis and a sudden fall in anti-MPO may predict a poor prognosis in some cases.