All are true regarding hereditary angioedema,except ?a) Dysfunction of enzyme is most common causeb) Enzyme involved is C1 INHc) C1 inhibitor targests Hageman factord) Complement C4 & C2 decreasee) Bradykinin level decrease during attack

Hereditary angioneurotic edema is due to deficiency of C1 inhibitor (C1 INH) or loss of function (dysfunction) of C1 inhibitor. Deficiency (85%) is more common than dysfunction (15%). C1 inhibitor targets and inactivates :- C1r and C1s (these two initiate the classical complement pathway). Factor XII a (Hageman factor) and kallikrein (both of these participate in contact activation of blood coagulation system. In C1 inhibitor deficiency, these enzymes can not be inactivated and two pathways (classical complement pathway and coagulation system) become unregulated and there is excessive production of bradykinin and C2 kinin. This leads to increased capillary permeability and angioedema. There is depletion of C2 to C4 level as they are consumed in unregulated classical complement pathway.