Mizoribine treatment for antihistamine-resistant chronic autoimmune urticaria.

Chronic autoimmune urticaria is routinely diagnosed using an autologous serum skin test. Mizoribine is a newly developed immunosuppressive agent that has low toxicity. The pharmacological effects of mizoribine are similar to those of another purine biosynthesis inhibitor, mycophenolate mofetil. A 57-year-old woman presented with recurrent wheals and was insufficiently managed with administration of antihistamines, antileukotrienes, oral corticosteroids, and cyclosporine. She was positive in the autologous serum skin test. Oral mizoribine therapy was started as a combination therapy with prednisolone. The patient achieved a dramatic improvement in symptoms and complete resolution of the urticaria a few days after adding mizoribine to her treatment. The prednisolone was tapered after the start of mizoribine treatment. Her symptoms did not flare up, and no side effects were observed. In vitro basophil histamine release assays suggested that she might have anti-IgE autoantibody-type histamine release activity. We believe that mizoribine has a therapeutic role in some patients with chronic autoimmune urticaria and may be useful for treatment of cases not responsive to classical therapy. We suggest that mizoribine might help to reduce anti-IgE autoantibody acting on the surface of basophils in chronic autoimmune urticaria.