Deep Phenotyping of CIndU

Chronic inducible urticaria (CIndU) is a group of skin disorders defined by recurrent itchy or burning wheals or angioedema that recur for more than six weeks with a specific triggering factor. This is different from chronic spontaneous urticaria which does not have a specific triggering factor. CIndU is subclassified in nine subtypes with each having its own specific trigger. These subtypes are further divided in physical urticarias (symptomatic dermographism, cold urticaria, delayed pressure urticaria, solar urticaria, heat urticaria, vibratory angioedema) or non-physical urticarias, i.e., cholinergic urticaria, aquagenic urticaria, and contact urticaria. Symptomatic dermographism (SD) is the most prevalent subtype of the physical urticarias. Its prevalence in Western populations is estimated to be between 1-5%. Following SD, cold urticaria (ColdU) is the next most common form, its annual incidence is estimated to be 0.05%. In this study, patients with the ColdU and symptomatic SD subtypes will be enrolled. As of yet, disease diagnosis of SD and ColdU is mostly purely clinical (clinical picture + patients' history), as there is a lack of objective biomarkers. Currently only two objective tools are available for the diagnosis of SD and ColdU, which are the FricTest and Temptest (both provocation tests). In addition, there is a lack of objective biomarkers for the prediction of treatment response and for the monitoring of treatment effects, as this is nowadays only monitored by patient reported outcomes.