Not all chronic urticaria is “idiopathic”

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Abstract
The aetiology of chronic urticaria in the majority of patients is elusive. The cause of physical urticarias (dermographism, delayed pressure urticaria, cold urticaria) is unknown. We have identified a subset of chronic "idiopathic" urticaria patients, representing approximately 30% of the total in which the disease is caused by the presence of IgG autoantibodies against the high affinity IgE receptor (FcepsilonRIalpha). This functional autoantibody stimulates normal (albeit vicarious) activation of mast cells and basophils via FcepsilonRI, causing whealing and angioedema. Anti-FcepsilonRI-positive patients are recognized by a combination of autologous serum skin testing and evoked histamine release from basophils of normal human donors. Autoantibody-positive and -negative patients are clinically indistinguishable and are treated routinely by combinations of H1 and occasionally H2-antihistamines in both cases. However, severely affected patients who are anti-FcepsilonRI-positive can also be treated by non-specific immunotherapy (plasma pheresis, intravenous immunoglobulin, cyclosporin.