-463 G/A myeloperoxidase promoter polymorphism is associated with clinical manifestations and the course of disease in MPO-ANCA-associated vasculitis.

Wegener's granulomatosis, microscopic polyangiitis, and Churg Strauss syndrome are forms of systemic vasculitides in which neutrophils and monocyte macrophages infiltrate the walls of small blood vessels, leading to destruction and occlusion. These diseases are associated with autoantibodies directed against granular components of neutrophils and monocytes, i.e., antineutrophil cytoplasmic antibodies (ANCA). The most common target antigens of ANCA in these vasculitides are myeloperoxidase (MPO) and proteinase 3 (PR3). ANCA-stimulated neutrophils injure endothelial cells, a process that is dependent upon the production of reactive oxygen radicals and the release of granular components such as MPO and PR3. Here we investigate whether a common functional MPO promoter polymorphism (-463 G/A) is associated with increased incidence and clinical aspects of ANCA-associated small vessel vasculitis. Genotyping was carried out for 142 patients with ANCA-associated small vessel vasculitis and 129 ethnically matched controls. The GG genotype was found to be associated with an increased risk for MPO-ANCA-associated vasculitis in females (86% GG, P = 0.045), but not males (64% GG, P = 1.0). Interestingly, the MPO A allele is associated with an increased incidence of relapses (P = 0.012) and an earlier age at diagnosis (P = 0.03) of MPO-ANCA-associated vasculitis. Both these associations are specific for MPO-ANCA and are not observed in patients with PR3-ANCA-associated vasculitis. These findings suggest that MPO expression levels influence the disease course of MPO-ANCA-associated vasculitis and further support the view that genetic factors are involved in the pathophysiology of this autoimmune disease.