MRGPRX2 and chronic idiopathic urticaria: Indeed, overexpression of MRGPRX2 and/or increased numbers of MRGPRX2+ MCs have been described in the lesions of patients with MC-driven disorders, e.g., cutaneous mastocytosis (13), chronic spontaneous urticaria (CSU) (15), and chronic prurigo (23), and correlated with disease severity in the latter.