ICD-11 definition : Hereditary angioedema is caused in the majority of cases by genetically determined
low absolute (type I) or functional (type II) levels of C1 inhibitor, a plasma proteinase
inhibitor involved in regulation of complement activation. It is characterized clinically
by recurrent subcutaneous and/or submucosal oedema and can result in life-threatening
laryngeal obstruction. Involvement of the digestive tract commonly causes abdominal
pain. This and the absence of accompanying urticarial weals or itch distinguish it
from the common form of angioedema, which is part of the spectrum of urticaria.;
Hereditary angioedema is caused in the majority of cases by genetically determined
low absolute (type I) or functional (type II) levels of C1 inhibitor, a plasma proteinase
inhibitor involved in regulation of complement activation. It is characterized clinically
by recurrent subcutaneous and/or submucosal oedema and can result in life-threatening
laryngeal obstruction. Involvement of the digestive tract commonly causes abdominal
pain. This and the absence of accompanying urticarial weals or itch distinguish it
from the common form of angioedema, which is part of the spectrum of urticaria.