Prevalence and clinical significance of antineutrophil cytoplasmic antibody in Graves' patients treated with propylthiouracil.

Development of antineutrophil cytoplasmic antibody (ANCA) during therapy with propylthiouracil (PTU) is not uncommon and PTU-induced ANCA-positive vasculitis is also reported. The aim of this study was to assess the presence and clinical significance of ANCA positivity in Graves' patients treated with PTU. Newly diagnosed Graves' disease patients (prospective group, n = 58) were evaluated before and during therapy with PTU to investigate the development of ANCA positivity. ANCA positivity is also investigated in previously diagnosed Graves' patients who had already been receiving PTU treatment (cross-sectional group, n = 51). Comparisons with Hashimoto thyroiditis (n = 55) and toxic nodular goitre (n = 20) patients, and healthy control subjects (n = 20) were carried out to define the possible influence of hyperthyroidism and/or thyroid autoimmunity on ANCA positivity. At baseline evaluation, ANCA was negative in all newly diagnosed Graves' patients. Only 28 of the 58 patients in prospective group completed 2 years of follow-up which occurred at 3-month intervals. ANCA positivity was detected 32.1% (n = 9) in a mean period of 11.7 +/- 6.1 months in prospective group. Only two (3.9%) patients in a cross-sectional group had ANCA positivity in a mean treatment period of 7.6 +/- 4.6 months. None of the patients with ANCA positivity developed symptoms and signs related to vasculitis. None of the patients with Hashimoto thyroiditis and toxic nodular goitre, and healthy control subjects had ANCA positivity. PTU therapy is associated with asymptomatic production of ANCA in a time-dependent manner, which mostly disappears after discontinuation of therapy. Hyperthyroidism or autoimmunity per se does not appear to have effect on development of ANCA positivity.