High prevalence of antineutrophil cytoplasmic antibody positivity in childhood onset Graves' disease treated with propylthiouracil

Propylthiouracil (PTU)-induced antineutrophil cytoplasmic antibody (ANCA)-r elated vasculitis and nephritis were recently reported in about 30 patients with hyperthyroidism. The objective of this study was to clarify the preva lence of ANCA and the relationship between ANCA and thyroid antibodies in c hildren with Graves' disease. Titers of myeloperoxidase (MPO)-ANCA in sera of 51 patients with childhood onset Graves' disease (16 before treatment, 25 and 10 treated with PTU and methimazole, respectively) were measured by enzyme-linked immunosolvent ass ay. Antithyroglobulin antibodies (TGAbs) and antithyroperoxidase antibodies (TPOAbs) were also measured by RIA in 25 PTU-treated patients. No patients had clinical manifestations of vasculitis and nephritis. MPO-ANCA was posi tive in 6.7% of patients before treatment and in 64.0% of those treated wit h PTU and in none of those treated with methimazole. MPO-ANCA had a signifi cantly positive correlation with TGAbs (P < 0.05) and no significant correl ation with TPOAbs. These findings show the high prevalence of the MPO-ANCA positivity in PTU-t reated childhood onset Graves' disease, suggesting that PTU may not be pref erred as the first line for the treatment of children with Graves' disease. The significant correlation between MPO-ANCA and TGAbs indicates that the severity of Graves' disease may be a factor responsible for the MPO-ANCA po sitivity. The crossreactivity between MPO-ANCA and TPOAbs may not play a ro le in the high prevalence of MPO-ANCA in the patients exposed to PTU.