Association between thyroid disease and its treatment with ANCA small-vessel vasculitis: a case–control study

Background. Case reports have described the onset of antineutrophil cytoplasmic antibody (ANCA)-associated small-vessel vasculitis (ANCA SVV) with use of anti-thyroid agents, but an association with thyroid disease in general has not been described. This association was evaluated in a southeastern US population-based case–control study. Methods. Cases (n = 158) had ANCA SVV with biopsy-proven glomerular involvement. Controls (n = 99) were frequency matched by age, gender and state. Use of drugs and comorbidities prior to diagnosis of ANCA SVV were assessed by telephone interview. Information on medications used for thyroid conditions was available in a subset of cases (n = 129). Logistic regression models were used to estimate adjusted odds ratios (OR) and 95% confidence intervals (CI). Estimates among females were also of interest. Results. History of thyroid disease was reported in 31 cases (20%) and 7 controls (7%) (OR = 3.7; 95% CI 1.5–9.2; P = 0.005); among females 25/65 (38%) cases and 5/53 (9%) controls (OR = 5.6; 95% CI 1.9–16.8; P = 0.002). Use of anti-thyroid agents was reported in 2 cases and 0 controls (OR not calculable). Among cases, myeloperoxidase (MPO)-ANCA was more common (86%) than proteinase 3 (PR3)-ANCA in those with a history of thyroid disease than those without (53%) (P = 0.007). Conclusions. Thyroid disease was associated with ANCA SVV, especially among women, and was most frequently associated with MPO-ANCA. The specific diagnosis and detailed clinical history of thyroid disease were not known; a limitation of the study. Use of anti-thyroid agents was uncommon. The association of thyroid disease with ANCA SVV may reflect a propensity for autoimmune disease.