Drug-associated antineutrophil cytoplasmic antibody-positive vasculitis - Prevalence among patients with high titers of antimyeloperoxidase antibodies

Objective. The triggers that induce antineutrophil cytoplasmic antibody (AN CA)-positive vasculitis (APV) are largely unknown. However, there have been reports suggesting that hydralazine, propylthiouracil, and several other d rugs may cause some cases of APV, and the majority of these cases have been associated with antimyeloperoxidase (anti-MPO) ANCA, Our experience led us to hypothesize that cases of high titers of anti-MPO antibodies are often drug-associated. Methods. In this study, we determined the prevalence of exposure to hydrala zine, propylthiouracil, and other drugs previously implicated in APV among 30 patients with vasculitis and the highest titers of anti-MPO antibodies n ewly detected in our laboratory between 1994 and 1998, The clinical, histol ogic, and other serologic features of these 30 patients were also examined. Results. The 30 study patients accounted for 12% of the 250 new patients wi th APV and anti-MPO who were tested during the study period, All 30 study s ubjects had anti-MPO titers that were more than 12 times the median titer o f the 250 patients. Ten (33%) of the 30 patients had been exposed to hydral azine and 3 (10%) had been exposed to propylthiouracil, An additional 5 pat ients (17%) had been exposed to 1 of the other previously reported candidat e drugs: 2 to penicillamine, 2 to allopurinol, and 1 to sulfasalazine, One of the patients exposed to hydralazine had also been exposed to allopurinol , In all cases, the clinical and histologic findings were typical of APV. T here was a strong association between the presence of antielastase and/or a ntilactoferrin antibodies and exposure to candidate drugs. Conclusion. These data suggest that a sizable proportion of cases of APV wi th high titers of anti-MPO antibodies are drug-associated, especially follo wing exposure to hydralazine or propylthiouracil. We recommend that the use of these drugs should be sought in cases of anti-MPO-positive vasculitis, particularly among patients with high titers of these antibodies.