Diagnosis and investigations


Pointers to a diagnosis of hereditary angioedema (HAE) can be:

  • Family history – other family members have had similar symptoms
  • Recurrent episodes of swelling (without hives) lasting more than 24 hours and unresponsive to antihistamines
  • Recurrent unexplained abdominal pain
  • Symptoms starting in childhood and worsening in adolescence.


For diagnosis of HAE types I and II
Serum C4 levels – usually low in untreated HAE.

If C4 is low, measure C1 INH level and function. If C4 is normal but HAE is suspected, measure C1 INH levels and function, and if normal, repeat C4 levels during an attack and assess C1 INH level and function if abnormal.

Genetic testing may be done in some cases where there is doubt.

HAE with Normal C1 Inhibitor
C4 and C1 INH levels are normal.
Diagnosis is from the clinical picture.
Kininogenase activity measurement and genetic analysis for F12 gene mutation may be considered.

Testing children for HAE

Symptoms of HAE are less common in babies and very young children, but swellings do occur and very occasionally may be severe.

HAE experts recommend testing children for HAE at the age of one year, as tests are less accurate before then. However, genetic testing is possible and may be done on blood taken from the umbilical cord at birth.

Testing relatives

If you receive a positive diagnosis for HAE, it is essential that close relatives are tested, whether or not they exhibit symptoms at the present time.

HAE is a very rare condition and patients should ideally be under the care of a HAE specialist in an accredited HAE centre. This will help to ensure that patients can achieve the best possible management of their condition. Please contact HAE UK for information about your nearest HAE specialist centre.