Objective: Antineutrophil cytoplasmic antibody (ANCA) has been well documented in association with propylthiouracil (PTU), and some patients with PTU-induced ANCA also develop clinical vasculitis. The aim of the current study was to detect ANCA specificities in sera from patients with PTU-induced ANCA with and without clinical vasculitis.
Methods: Sera from 65 patients with PTU-induced ANCA were collected, and 27 of these patients were diagnosed with PTU-induced ANCA associated systemic vasculitis (AASV). Indirect immunofluorescence assay and antigen-specific ELISAs were used to detect ANCA and their antigen specificities. The seven known target antigens included myeloperoxidase (MPO), proteinase 3, human leukocyte elastase, lactoferrin, cathepsin G, azurocidin and bactericidal/permeability-increasing protein (BPI).
Results: In IIF assay, P-ANCA was found in 58/65 (89.2%) sera, C-ANCA in two, both P-ANCA and C-ANCA in five, respectively. MPO (60%) and lactoferrin (63.1%) were the two most common target antigens detected in sera from all the patients. 25/27 sera from patients with PTU-induced AASV recognized multiple target antigens, which was significantly higher than those (13/38) from patients without (P<0.001). Except anti-BPI antibodies, the prevalence of antibodies against the other six target antigens was significantly higher in patients with clinical vasculitis than that in patients without (P<0.05, respectively).
Conclusion: Antibodies against multiple ANCA specific antigens, especially the antigens rather than MPO and PR3, might be the characteristic of PTU-induced ANCA. Patients with antibodies against more ANCA specific antigens might be at increased risk of developing overt clinical vasculitis. The mechanism of ANCA production in PTU-induced cases was different from that in primary AASV.