Hereditary Angioedema with Normal C1 Inhibitor

Until recently it was assumed that hereditary angioedema was a disease that results exclusively from a genetic deficiency of the Cl inhibitor. In 2000, families with hereditary angioedema, normal Cl inhibitor activity, and protein in plasma were described. Since then, numerous patients and families with that condition have been reported. Most of the patients were women. In many of the affected women, oral contraceptives, hormone replacement therapy containing estrogens, and pregnancies triggered the clinical symptoms. In some families mutations in the coagulation factor XII (Hageman factor) gene were detected.