Preheated autologous serum skin test in localized heat urticaria

Localized heat urticaria (LHU) is a rare type of physical urticaria, characterized by itching and erythema and well-demarcated weals, appearing within minutes at heat-exposed body sites. Its pathogenesis has not yet been clarified. We report the case of a 46-year-old woman with a generalized form of LHU, which was induced by exposure to warm baths, and consumption of warm food and drinks. Weal reaction was obtained 10 min after application of a metal cylinder heated to 43 °C. Interestingly, only serum previously heated to 56 °C and injected intradermally for autologous serum skin test induced a weal and flare reaction, whereas serum preheated to 45 °C did not induce any reaction. Our patient did not respond to high-dose antihistamines, and refused a heat desensitization programme. Treatment with colchicine 1 mg/day or ciclosporin A 3.5 mg/kg/day for 1 month yielded no improvement. Mild improvement was obtained with intramuscular injection of triamcinolone acetonide 40 mg every 2 weeks for 2 months.