SERPING1 mutation update: Mutation spectrum and C1 Inhibitor phenotypes.

C1 inhibitor (C1Inh) deficiency is responsible for hereditary angioedema (C1-INH-HAE) and caused by variants of the SERPING1/C1INH/C1NH gene. C1Inh is the major control of kallikrein-kinin system. C1Inh deficiency leads to its uncontrolled activation, with subsequent generation of the vasoactive peptide bradykinin.

Hereditary C1 inhibitor deficiency is associated with high spontaneous amidase activity.

Background: Angioedema diagnosis classically targets the complement system (via C1 inhibitor (C1Inh) function and antigenic C4 level) and contact phase activation (via amidase activity). Bradykinin is responsible for angioedema attacks and is produced from contact phase activation secondary to failed C1Inh control.

Objective: We aimed to compare the diagnostic performances of spontaneous amidase activity and antigenic C4 level in C1Inh hereditary angioedema (C1Inh-HAE) patients.