Immune stimulus exposure as a trigger for the development of chronic pruritus and circulating blood Type 2 inflammation.

Background Chronic pruritus (CP) is a poorly characterized condition associated with intense pruritus without a primary skin eruption. This condition tends to emerge more commonly in older adults, and there is limited research on triggering factors. Objective To explore the clinical characteristics and pathophysiology of chronic pruritus following exposure to an immune stimulus. Methods Clinical characteristics and plasma samples were collected from 15 patients who developed CP following an immune stimulus such as checkpoint inhibitors or vaccination. A multiplex panel was used to analyze plasma cytokine concentrations within these patients. Results Most immunotherapy-treated patients experienced CP during treatment or after 21 to 60 days of receiving treatment, while vaccine-stimulated patients developed pruritus within a week of vaccination. Plasma cytokine analysis revealed elevated levels of twelve cytokines in patients with immune-stimulated CP compared to healthy controls. Notably, Th2-related cytokines IL-5 (FC 2.65; q<0.25) and TSLP (FC 1.61 q<0.25) were upregulated. Limitations Limitations of this study include limited sample size, particularly in the plasma cytokine assay. Conclusions and Relevance This study reveals triggers of CP development and describes alterations in blood Th2 markers in CP patients, including IgE, increased blood eosinophils, and cytokines IL-5 and TSLP.