Clinical and histological features of antineutrophil cytoplasmic antibody-associated vasculitis related to antithyroid drugs

Background: Antithymid drugs such as propylthiouracil and methimazole have been reported to cause antineutrophil cytoplasmic antibody (ANCA)-associated vasculitis (AAV), but little is known about long-term outcomes. Materials and methods: We identified AAV patients who underwent renal biopsy and retrospectively assessed their clinical and histological findings. Patients with AAV who had received propylthiouracil or methimazole were defined as having antithyroid drug-associated AAV (ATD-AAV), and the other patients were defined as having primary' AAV. Results: Seven patients with ATD-AAV and 83 patients with primary AAV were identified. Compared with the primary AAV group, the patients with ATD-AAV were significantly younger (mean +/- standard deviation; 45.4 +/- 21.4 years vs. 65.9 +/- 13.8 years, p < 0.01), and had lower serum creatinine (median [intcrquartile range]; 0.7 mg/dL [0.6 -1.5] vs. 2.3 ing/dL [1.0 - 4.0], p = 0.02), as well as a higher frequency of positivity for MPO-ANCA/ PR3-ANCA (42.9 vs. 4.8%, p < 0.01). While glomerular crescents varied, interstitial fibrosis and tubular atrophy were milder in ATD-AAV patients. Kaplan-Meier analysis showed a significantly higher kidney survival rate in patients with ATD-AAV than in those with primary AAV (p = 0.05). Conclusion: Patients with ATD-AAV were younger and had milder kidney involvement, resulting in a better long-term outcome compared with primary AAV.