<prompt> 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 attackabceae  <response>: 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. 