Progress and Challenges in the Understanding of Chronic Urticaria

Chronic urticaria is a skin disorder characterized by transient pruritic weals that recur from day to day for 6 weeks or more. It has a great impact on patients' quality of life. In spite of this prevalence and morbidity, we are only beginning to understand its physiopathology and we do not have a curative treatment. Moreover, a patient with chronic urticaria may undergo extensive laboratory evaluations seeking a cause only to be frustrated when none is found. In recent years there have been significant advances in our understanding of some of the molecular mechanisms responsible for hive formation. The presence and probable role of IgG autoantibodies directed against epitopes expressed on the alpha-chain of the IgE receptor and to lesser extent, to IgE in a subset of patients is generally acknowledged. These autoantibodies activate complement to release C5a, which augments histamine release, and IL4 and leukotriene C4 are released as well. A perivascular cellular infiltrate results without predominance of either Th1 or Th2 lymphocyte subpopulations. Basophils of all chronic urticaria patients (autoimmune or idiopathic) are hyperresponsive to serum, regardless of source, but poorly responsive to anti IgE. In this review we will summarize the recent contributions to this field and try to provide insights to possible future directions for research on this disease.