Cholinergic Urticaria: Clinical Presentation and Natural History in a Tropical Country

BACKGROUND: Cholinergic urticaria (CholU) is a subset of chronic inducible urticaria characterized by the recurrent pinpoint-sized wheals that are induced by exercising or increasing core body temperature. Currently, the data of CholU in tropical climate is still limited. OBJECTIVE: To investigate the clinical features and natural course of CholU in a tropical country. MATERIALS AND METHODS: This retrospective chart review study analyzed the data of CholU patients aged over 18 years who visited Siriraj Urticaria Clinic, Siriraj Hospital, Bangkok, Thailand, between January 2007 and September 2019. Demographic data, clinical presentations, and results of provocation tests and other laboratory investigations were evaluated and compared with other studies reported in temperate zones. RESULTS: Sixteen out of 2,175 chronic urticaria patients (0.7%) were diagnosed with CholU. The median age of CholU patients was 28.0 ± 11.7 years with male predominance (56.3%). Three patients (18.8%) had a history of atopy. Fifteen patients (93.8%) were positive to the exercise provocation test. Nonsedating antihistamine drugs were a main treatment (73.8%). Six patients (37.5%) were in remission at the time of the study, with a mean duration 4.3 years. The Kaplan-Meier survival analysis demonstrated that 12.5%, 35.5%, and 67.9% of patients would have disease remission within 1 year, 5 years, and 13 years, respectively. CONCLUSIONS: The prevalence of CholU differs in each geographic region and is found to be low in tropical countries with a median duration 4.3 years. The prevalence of atopy and anaphylaxis with CholU is also lower in tropical countries than in temperate.