Down regulation of the high-affinity IgE receptor associated with successful treatment of chronic idiopathic urticaria with omalizumab

While approximately 20% of the population will experience an episode of acute urticaria at some point in their lifetime, only 0.1% will experience the scourge of chronic urticaria [1]. This disease is characterized by at least 6 weeks of almost daily episodes of intensely pruritic cutaneous wheals that typically last less than 24 hours and are not associated with residual pigmentation. Half of patients with chronic urticaria are thought to have this disease as a result of autoimmune phenomenon, while the remaining patients are designated as having "idiopathic" disease. It has been estimated that approximately 35-45% of patients possess autoimmune IgG antibodies that target the alpha subunit of FcεRI or, to a lesser extent, target directly the IgE antibody [2]. A link between thyroid autoimmunity and chronic urticaria has also been observed in a subset of patients [3]. Consequently, the evaluation of patients with chronic urticaria may include investigating for thyroid dysfunction and for the presence of microsomal antibodies and/or anti-thyroperoxidase antibodies.Treatment of patients with chronic urticaria, autoimmune or idiopathic, involves targeting the H1 receptor with sufficient doses of antihistamines that will control the patient's symptoms. When symptoms can not be controlled with maximal doses of antihistamines, immunosuppressive medications such as corticosteroids or cyclosporine are often employed. However, the potential short and long term side effects from these medications make their use less than desirable for both the clinician and patient. Omalizumab is a recombinant monoclonal antibody that selectively binds to IgE and inhibits its binding to FcεRI on the surface of mast cells and basophils. The beneficial effects of this therapy in the treatment of moderate to severe persistent asthma have been well documented [4]. However, the off-label use of omalizumab for treatment of chronic urticaria has shown promise and represents an immunosuppressive spar