Clinical features and natural history of physical urticaria in children

Physical triggers are the most common precipitating factors for chronic urticaria in childhood. We investigate the natural history of physical urticaria (PU) and attempt to identify prognostic features. A retrospective study covering a 3 yr period (1999-2002) identified 82 children with PU seen in a tertiary referral centre. Parents of 53 children with PU responded to follow up by questionnaire and were included in the data analysis. The questionnaire ascertained symptom severity, remission status, effects of treatment and prognostic factors in determining resolution of the urticaria. Not all parents answered every question. Fisher's exact test was used to compare the remission and non-remission groups and Kaplan-Meir survival analysis was used to derive estimates of time to achieve remission. All 53 children with PU had chronic urticaria, with dermatographic, cholinergic and mixed subtypes of PU forming over 70% of the subtypes. Overall, 13% (6/45) of the children reported respiratory symptoms with the episodes of urticaria, and 67% (35/52) reported associated angioedema. In univariate analysis, a history of other allergic conditions in the child was associated with a greater chance of non-remission (p = 0.007). No significant difference in the age of onset of urticaria and duration of individual bouts was noted between the remission and non-remission groups. Episodes of urticaria were significantly less frequent (p = 0.02) in the remission group (monthly/weekly/daily - 70%/30%/0%) than the non-remission group (38%/34%/28%). Among the 20 children achieving remission, on average this occurred 30 months after onset of symptoms. In the survival analysis, the number of children becoming urticaria free was 11.6% (95% CI: 5.4%-23.9%) at 1 yr post-onset and 38.4% (95% CI: 25.9%-54.3%) 5 yr post-onset. In conclusion, based on this selected tertiary population, the prognosis for PU may not be as benign as has previously been reported. A history of allergic conditions and more frequent episodes of urticaria were associated with a poorer prognosis.