An unusual cause of angioedema

C1 esterase inhibitor is a key regulatory protein involved in the complement and coagulation pathways, as well as in modulating inflammatory responses in the circulation.² One of its primary functions is to limit the production of bradykinin, a potent mediator of vascular permeability and vasodilation, causing swelling.³ C1 esterase inhibitor (C1-INH) deficiency leads to excessive bradykinin production, resulting in vasodilation and increased vascular permeability, which causes fluid leakage into tissues and the development of swelling and oedema.¹⁰