Action of Complement in Hereditary Angioneurotic Edema: The Role of C′1-Esterase *

The tendency to have severe attacks of localized alngioneurotic edema may be inherited as an au- tosomal dominant trait (1-7). The hereditary form of angioneurotic edema is also distinguishable by a biochemical abnormality in that affected per- sons lack detectable serum inhibitor of an enzyme derived from the first component of complement (C'1-esterase) (8). This serum deficiency is detectable before the onset of symptoms, which may appear at any time from 1 year of age to adult life. Although serum inhibitor of C'1- esterase is constantly absent from sera of patients, attacks of edema are episodic and self-limited and affect only circumscribed areas of the body. The present studies were undertaken to define changes in C'1-esterase and the components of complement in serum of patients during attacks of edema and during asymptomatic intervals.