Analysis of solar urticaria in Thai patients.

BACKGROUND Solar urticaria (SU) is an uncommon photodermatosis characterized by erythema and whealing within minutes to a few hours after exposure to sunlight or an artificial light source. OBJECTIVE To determine the clinical features, photobiological characteristics and treatment outcomes in Thai SU patients visiting a tertiary referral hospital. METHOD A retrospective analysis of 13 patients with SU was conducted. Demographic data, disease characters, phototesting results, laboratory investigations, treatment and outcome were evaluated. RESULTS Of the 13 patients diagnosed with SU from 2000 to 2012, most patients were female (10, 77%). The mean age of onset was 29 years (15-51). The mean duration of SU was 46 months (6-120) at presentation. The most common affected location was the upper extremities (92%), followed by head and neck (77%). The responsible action spectra were visible light in 8 patients (61.5%), ultraviolet A (UVA) in 1 patient (8%), and both visible light and UVA in 4 patients (31%). The median course from disease onset to disease resolution was 63 months (95% confidence interval 30-95). After 13 months and 55 months from the onset of symptoms, 23% and 49% of patients, respectively, were predicted to recover from their symptoms. CONCLUSION Solar urticaria is a rare condition in Thailand. The common eliciting spectra of SU were visible light and UVA. Management of SU remains challenging.