Chronic idiopathic urticaria: a family study

Background: Genetic factors play a pivotal role in the pathogenesis of many autoimmune disorders. Recent studies demonstrated that chronic idiopathic urticaria (CIU) is an autoimmune disease at least in a subset of patients, but familial studies have not yet been conducted. Objective: To investigate the familial pattern of CIU. Methods: One thousand three hundred eight adults with CIU (aged > 12 years; male/female 388/920) seen during the last 10 years were thoroughly interviewed to ascertain the presence of CIU among first-degree relatives. Positive histories were confirmed by medical recordings. Proportions were compared with those expected in the general population on the basis of a 0.1% prevalence of the disease. Results: Fifty-six of 1,308 (4%) patients had a familial history of CIU affecting at least one first-degree relative. This number exceeded by approximately eight times the expected one (P<0.001). Twenty-two of 23 (96%) patients with a positive familial history were positive on autologous serum skin test (P<0.01 by comparison with previous studies). Conclusion: The observation that CIU is much more frequent among first-degree relatives of affected individuals than in the general population suggests the existence of a genetic background for the disease and provides a clinical support to the reported association between CIU and human leukocyte antigen DR4. Ninety-six percent of patients with a positive familial history were positive on autologous serum skin test, a condition that has been associated with the presence of circulating histamine releasing factors, including anti-FcepsilonRI or anti-immunoglobulin E antibodies.