Alternating antineutrophil cytoplasmic antibody specificity - Drug-inducedvasculitis in a patient with Wegener's granulomatosis

We describe a patient who presented with Wegener's granulomatosis associate d with antineutrophil cytoplasmic antibodies (ANCA) directed against protei nase 3 (PR3) with a cytoplasmic immunofluorescence pattern (cANCA), whose A NCA type changed to antimyeloperoxidase antibodies with a perinuclear immun ofluorescence pattern (pANCA) when treated with propylthiouracil, and chang ed back to anti-PR3 antibodies with cANCA after the medication was disconti nued. The patient developed flares of vasculitis symptoms associated with r ises in either type of ANCA. Tests far antimyeloperoxidase ANCA were repeat edly negative before the drug was started, strongly implicating the drug as the cause of the episode. This case demonstrates that patients with idiopa thic ANCA-positive vasculitis may quickly develop a superimposed drug-assoc iated ANCA-positive vaseulitis. Iatrogenic vasculitis should be suspected w hen a patient with idiopathic vasculitis with one type of ANCA develops the other type of ANCA.