Observations on biochemical abnormalities in hereditary angioneurotic edema

Serum specimens collected from patients with hereditary angioneurotic edema showed low titers for inhibitors of serum kallikrein, and, when obtained shortly after an episode of edema, were deficient in available substrate for kallikrein activity. Patients were more sensitive to intradermal injection of serum kallikrein than normal controls. Serum also showed an abnormally low content of inhibitor for activated C′1-esterase, and the capacity of C′1-esterase to cause severe permeability-increasing reactions in human skin, and with special intensity in patients' skin, was demonstrated. Other skin tests suggested the possible participation in the edematous process of PF/Dil. The exact role of these permeability factors and the precise identity of the specific inhibitor(s) which are lacking or deficient remain uncertain.