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.

The objective of this study is to deep phenotype CIndU (subtype SD and ColdU) and detect novel biomarkers for diagnosis andtreatment response as well as establish methodologies for (non-) invasive monitoring of treatment effects in chronic inducible urticaria. For this purpose, a study with a multi-modal approach will be performed for in-depth characterization of SD and ColdU. The study willconsist of 2 parts: in part A the biology of disease will be investigated, and in part B the response of the biomarkers to real-world treatment with omalizumab will be monitored (part B). The former to characterize objectively measured disease characteristics and mechanisms underlying its development, the latter to monitor response of the disease and its characteristics to standard of care treatment once in four weeks. The study focusses on cellular, molecular, biophysical, imaging and microbiome analyses in comparisonwith chronic spontaneous urticaria (CSU) patients and matched healthy volunteers.