Myeloperoxidase is the primary enzyme that generates toxic oxygen radicals during cellular reactions, and anti-myeloperoxidase antibodies are autoantibodies that target myeloperoxidase in the cytoplasm as a target antigen. A strong positive anti-myeloperoxidase antibody is often a sign of necrotizing vasculitis or idiopathic crescentic glomerulonephritis. Positivity for this antibody can also be seen in other diseases rheumatic immune diseases such as polyarteritis nodosa, antiglomerular basement membrane disease, granulomatous polyangiitis, systemic lupus erythematosus, rheumatoid arthritis, pharmacologic lupus, and Felty’s syndrome. It can also be present in infections, drugs or thyroid and intestinal disorders. So anti-myeloperoxidase antibodies are an antibody test that can detect many of these diseases or confirm many diseases by testing for their own antibodies.”