C1 inhibitor: from complement system to bradykinin angioedema.

C1 Inhibitor (C1INH) is a crucial regulator of multiple plasmatic pathways, including complement, coagulation, kallikrein-kinin systems, and fibrinolysis. C1INH deficiency results in the downstream overproduction of the vasoactive peptide bradykinin (BK), the primary mediator of angioedema (AE), a rare disease characterized by unpredictable attacks of swelling in various locations of the body. C1INH deficiency can be hereditary (caused by a mutation in SERPING1 gene) or acquired (frequently underlying lymphoproliferative disease); C1INH level and functional assays are the golden standard for biological diagnosis of C1INH deficiency. Other forms of hereditary angioedema with normal C1INH activity are emerged in recent years. The most recent guidelines have issue recommendations for classification, clinical and laboratory diagnosis, and management of AE with and without C1INH deficiency. Current axes of research aim to discover new diagnostic and/or prognostic markers of BK-mediated angioedema as well as emphasize the link between C1INH deficiency and chronic comorbidity.