The antipsoriatic effect of thiamazole is not accompanied either by significant changes in blood lymphocyte subsets nor by serum concentration of TNF-alpha.

It has been reported that the antithyroid thiourethylenes, propylthiouracil and methimazole can bring about significant clinical improvement in patients with psoriasis vulgaris. In this paper, we reconfirmed the clinical usefulness of the antithyroid drug thiamazole, which is similar to methimazole, in Japanese patients with psoriasis vulgaris. We further asked whether the clinical improvement was linked to the changes in some immunological parameters or not. To answer this question, we analyzed peripheral blood lymphocyte subsets and measured serum concentrations of TNF-alpha and IL-1beta in 13 patients with psoriasis vulgaris before and during thiamazole administration. The mean percentage of CD4+ HLA-DR+ lymphocytes in the patients was constantly elevated before and 12 weeks after the administration. The patients treated with thiamazole showed a significant increase in the ratio of CD4+/CD8+ at the 4th week, though it declined at the 8th and 12th week. Other lymphocyte subsets showed no significant change during the treatment. The concentrations of serum TNF-alpha exhibited no significant change during thiamazole administration. Serum concentration of IL-1beta was under the detection level. These results indicate that thiamazole may improve the psoriatic lesion via other immune mechanisms, or the effects can not be reflected by the peripheral lymphocyte subsets and cytokine which we investigated.