The pathogenesis of chronic idiopathic urticaria
R. A. Sabroe and M. W. Greaves
St John's Institute of Dermatology, St Thomas' Hospital, London, England.
Chronic idiopathic urticaria (CIU) can be extremely disabling and difficult
to treat, with little response to antihistamine therapy. The pathogenic
mechanisms of the disease are not well understood, but the primary effector
cell is the mast cell. Release of mast cell mediators can cause
inflammation and accumulation and activation of other cells, including
eosinophils, neutrophils, and possibly basophils. Recent work has
demonstrated that about one third of patients with CIU have circulating
functional histamine-releasing autoantibodies that bind to the
high-affinity IgE receptor (Fc epsilon RI) or, less commonly, to IgE; mast
cell-specific histamine-releasing activity that has not yet been fully
characterized; no identifiable circulating histamine-releasing activity.
The mainstay of treatment of CIU consists of antithistamines, but
immunotherapy using plasmapheresis, intravenous immunoglobulin, and
cyclosporin may be valuable in severely affected patients with
treatment-resistant disease. The response to immunomodulation and the
recent finding of an association with HLA DR4 lend further support for an
autoimmune basis to CIU in some patients.
