Antineutrophil cytoplasmic antibodies: two cases of changing antigenic specificity

Abstract

The transformation of the antineutrophil cytoplasmic antibody (ANCA) specificity in the absence of specific drug treatment has not been reported in the literature. A few studies have suggested changes in the epitopes recognized by the ANCAs. We describe two patients who switched from myeloperoxidase-positive to PR3 ( proteinase 3)-positive ANCA during the course of their disease process and subsequently remained unchanged. One patient developed ulcerative colitis following the appearance of PR3-ANCA while the other remains quiescent. Regular follow-up and close monitoring of ANCA specificity are essential. A change of specificity may indicate the development of a new ANCA-related disease.

Incidence of PR3- and MPO-ANCA autoantibody specificity changes in ANCA-associated vasculitis

“…In some patients it has coincided with drug regime changes but this was not the case in any of our patients, who were all on standard maintenance or induction therapy. 4 There are a number of limitations to this study. Due to its long term (13 years) a number of different methodologies were used and may have accounted for some of the specificity switches as variability between ANCA assays is well recognised.…”

“…In some patients it has coincided with drug regime changes but this was not the case in any of our patients, who were all on standard maintenance or induction therapy. 4…”

“…It is normal practice in follow up of patients during treatment and remission to perform both PR3-ANCA and MPO-ANCA, regardless of the previous results observed or the current IIF pattern, as there have been a number of cases described in which autoantibody specificity has switched between PR3-ANCA and MPO-ANCA. 4 Though considered unusual, the incidence of antibody specificity switching has not been reported in a large case series, published data being limited to a few case reports summarized in Saleem et al. 4 Here we present data from a case series of 218 patients with AAV spanning nearly 13 years of practice.…”

“…4 Though considered unusual, the incidence of antibody specificity switching has not been reported in a large case series, published data being limited to a few case reports summarized in Saleem et al. 4 Here we present data from a case series of 218 patients with AAV spanning nearly 13 years of practice.…”