Differential Effects of Dupilumab in a Patient With Localized Heat Urticaria, Delayed Solar Urticaria, and...

Physical urticaria is a subtype of chronic inducible urticaria characterized by wheals and/or angioedema triggered by physical stimuli. We report a refractory case of combined localized heat urticaria, delayed solar urticaria, and symptomatic dermographism in a 16-year-old girl. Provocation testing showed erythematous and edematous lesions after thermal stimulation at 42°C and after the application of warm water at 40°C and 42°C. An intradermal test using the patient's serum heated to 42°C for 5 min yielded a positive result, leading to the diagnosis of localized heat urticaria. Visible light irradiation induced no immediate wheals; however, wheals developed at all irradiated sites 4.5 h later, accompanied by intense pruritus without burning sensation or pain, consistent with delayed solar urticaria. A FricTest provoked wheals, confirming symptomatic dermographism. Antihistamines were ineffective, and omalizumab, administered as a second-line treatment, improved only the symptomatic dermographism, with no effect on the heat or solar urticaria. Dupilumab was subsequently administered 12 times. Repeated provocation testing during treatment showed resolution of symptomatic dermographism, whereas localized heat urticaria persisted and delayed solar urticaria showed no meaningful improvement. The Urticaria Control Test score also did not improve. These findings suggest that the pathogenesis of symptomatic dermographism in this case may involve IgE- and IL-4/IL-13-mediated pathways, whereas localized heat urticaria and delayed solar urticaria may be driven by distinct mechanisms.