Autoimmune urticaria

That a subset of patients with chronic idiopathic urticaria possesses functional autoantibodies against the high affinity IgE receptor, or less commonly, IgE, is widely accepted. That these same autoantibodies are causative of chronic urticaria is highly probable, but not entirely proven, since no animal model of chronic urticaria has been devised using these autoantibodies. However we know that intradermal injection of anti-FceR1 IgG in healthy volunteers does cause an urticarial reaction. The concept of chronic urticaria as a disease caused by autoantibodies activating the normal function of target cells (mast cells) by combination with a receptor epitope is intriguing, although not entirely unique, since a similar mechanism appears to underlie some types of autoimmune hyperthyroidism. The detection of patients with these antibodies is usually not possible by clinical assessment alone. Unfortunately no convenient or reliable immunoassays have been developed to detect the autoantibodies, and the gold standard remains the basophil mediator release assay, using normal human donor basophils or a basophil leukemia cell line. The autologous serum skin test has proved to be a useful screening test for autoimmune urticaria. Identification of patients with autoimmune urticaria is of some importance because, apart from obviating the necessity for irrelevant tests, immunotherapy, using cyclosporin, intravenous immunoglobulin or even plasmapheresis can be contemplated in severely affected treatment-resistant patients.