Hereditary angioneurotic edema is due to -

The deficiency of C1 inhibitor is associated with hereditary angioneurotic edema. It is a condition characterised by episodic angioedema of the subcutaneous tissues or of the mucosa of the respiratory or alimentary tracts. Fatal if larynx or trachea affected. Attack is precipitated by local exhaustion of the reduced amount of the C1 inhibitor present ,leading to the autocatalytic activation of C1 and unrestrained breakdown of C4 and C2. Reference : Anathanarayan & paniker's 9th edition, pg no: 126 <\p>