URTICARIA IN CHILDREN

Urticaria - Thyroid autoimmunity and chronic urticaria
Urticaria is common in adults, with up to 25% reporting episodes at least once, but is less common in children, affecting up to 7% of children. Most cases of urticaria in children are acute, lasting less than 6 weeks. Common etiologies for acute urticaria in children include allergen exposure (e.g., drugs, food) and infection. The etiology of chronic urticaria, lasting more than 6 weeks, is usually more difficult to determine. In adult studies, up to 50% of cases of chronic, idiopathic urticaria are attributable to the presence of autoantibodies against the
-chain of the high affinity IgE receptor on mast cells and basophils. These antibodies have been found in 3 of 7 children 10 to 16 years of age in one series, but larger series are not available. Antithyroid antibodies are frequently identified in patients with chronic, idiopathic urticaria, but are thought to serve as markers of autoimmunity rather than play a direct pathogenic role. A recent evaluation of data from 187 patients with chronic urticaria, aged 7 to 17 years, referred to an allergy clinic over a 7 1⁄2-year period, identified 8 children with thyroid autoantibodies. Of the 8 patients, 5 were euthyroid, 1 had previously been diagnosed with Hashimoto’s thyroiditis, and 2 were diagnosed as hypothyroid during the urticaria evaluation, one 5 years after the onset of urticaria. The two hypothyroid patients were treated with thyroxine replacement without resolution of the urticaria. Periodic evaluation of thyroid function and anti-thyroid antibodies should be practiced for children with chronic, idiopathic urticaria. Euthyroid patients with antithyroid antibodies should also be observed with periodic evaluations of thyroid dysfunction.

Acquired cold urticaria in children
Acquired cold urticaria is thought to be an uncommon form of physical urticaria in children, but the prevalence has not been well characterized. Triggers for urticaria/angioedema in these patients include cold weather (usually exposed areas), cold objects, and aquatic activities. Fatalities have been reported from anaphylaxis and drowning. Characteristics of a group of 30 patients with acquired cold urticaria less than 18 years of age were recently reported. Among the 30 patients, the mean and median age of onset was 7 years. Only two patients (7.4%) had resolution of the cold urticaria and only 9 (33.3%) showed improvement during the follow up period. Although the duration of follow-up was limited in this series, acquired cold urticaria should be considered a chronic, persistent disorder. Evaluation for systemic etiologies, including cryoglobulinemia, was negative in all cases. Significantly, one third of the patients in the series had experienced anaphylactic reactions from cold exposure. Identification of patients with cold urticaria is critical to allow provision of appropriate recommendations for management and selfinjectable epinephrine devices. Based on the findings of this series, acquired cold urticaria can be seen in patients as young as 2 years old.