If the patient has recurrent episodes of edema affecting the limbs, face, neck or buttocks and lasting several hours to days, HAE should be considered as a diagnosis. HAE can also be the cause of recurrent colicky pain in the abdominal cavity.
If a family history is already known to include cases of HAE, it is very reasonable to suspect HAE the first time it occurs in another family member.
Failure to respond to drugs administered for allergic reactions, such as antihistamines, corticosteroids and adrenaline, is also used to distinguish HAE from allergic edema.
However, the diagnosis of HAE is confirmed by special blood tests in which the concentration and activity of C1-INH and the concentrations of other proteins in the complement system are measured. The concentration and/or activity of C1-INH are reduced in patients with HAE.