Chronic idiopathic urticaria

Synonyms and keywords: CIU

Overview
Chronic idiopathic urticaria (CIU) is defined as frequent (daily, or near daily) itching and wheals for 6 weeks or more in the absence of any known cause. The incidence is approximately 0.5% of the population.

Pathophysiology
There are 2 subgroups of patients.

Autoimmune chronic urticaria (AICU)
30%-50% of patients have IgG autoantibodies against either the high-affinity IgE receptor FcεR1 or, less commonly, IgE. These patients also have an increased risk of antithyroid autoantibodies. Establishing this diagnosis is helpful as these patients may benefit from immunotherapy.

Truly idiopathic chronic idiopathic urticaria
In 50% of patients no autoantibodies are detected.

Symptoms
About 90% of patients also have angioedema.

Laboratory studies
There are no convenient readily available diagnostic studies.