Are there different forms of life in the antineutrophil cytoplasmic antibody universe?

For some autoimmune diseases, autoantibodies and their target antigen specificity can provide information about pathogenic mechanisms and disease phenotypes. What do antineutrophil cytoplasmic antibodies (ANCAs) tell us about a patient with vasculitis? Do ANCAs or their antigen specificity identify patients whose vasculitis differs in its clinical expression and relapse potential? If so, could this information guide treatment? Two articles in this issue address these questions. © 2005 American College of Physicians.