[Chronic urticaria and Hashimoto-Hashimoto's thyroiditis: report of 6 cases]

Chronic urticaria is a common skin disorder. The cause is rarely determined. Autoimmune diseases, particularly autoimmune thyroiditis, have been implicated in the occurrence of chronic urticaria.

We reviewed clinical records of patients with Hashimoto's disease and chronic urticaria.

In our department, six patients had presented chronic urticaria associated with Hashimoto's thyroiditis: four patients, of which three treated with L-thyroxine were euthyroid, the other two were hypothyroid. Hashimoto's thyroiditis had been diagnosed for three patients during the investigation of chronic urticaria. Three patients developed chronic urticaria though they were treated with thyroid suppression for Hashimoto's disease. Two of them had a dramatic improvement with opotherapy. One patient who was euthyroid without treatment improved with hormonal therapy. The fourth patient had a partial remission with thyroid hormones and was cured with corticotherapy.

The mechanism by which thyroid autoimmunity is associated with urticaria is poorly understood. A cross-linking of IgE receptors of mastocytes induced by antithyroid antibodies may be a cause of histamine release. Hormonal therapy may be a potent event for the clinical improvement by the suppression of chronic thyroid stimulation. Assay of thyroid hormone and antithyroid antibodies should be performed in patients with chronic urticaria. Discovery of Hashimoto's thyroiditis with chronic urticaria requires thyroid hormone replacement not only in hypothyroid but also euthyroid patients.