Diagnosing HAE
Hereditary
angioedema (HAE) is a rare disease that is often misdiagnosed because
its symptoms mimic those of several common conditions, such as allergic reaction,
acute appendicitis, gallbladder attack, submucosal abdominal tumor, diverticulitis,
and irritable bowel syndrome.1,2
When a family history is not available, initial misdiagnosis commonly occurs. In
these cases, patients are often subjected to non-essential medical procedures, such
as laparoscopy; ineffective treatments, such as administration of antihistamines;
and/or unnecessary psychiatric referrals (due to "unexplained" recurrent abdominal
pain). 1,6
HAE can be confirmed with proper blood tests
When HAE is suspected, a referral to an allergist/clinical immunologist for definitive
diagnostic procedures and treatment is appropriate, because not all physicians have
experience with HAE and not all laboratories are equipped to handle the necessary
blood specimens. 8
Patients should have serum levels of C4 measured. A low serum C4 level (C4 <30%
of mean normal level) is an excellent screening test, because C4 levels are invariably
low in untreated patients with either type I or type II HAE.
6
When these values are low (C4 <30% of mean normal level), antigenic C1-INH levels
should be tested.
Clinical and laboratory findings associated with angioedema of various causes 6
|
Type of Angioedema
|
Clinical Findings
|
C4 Level
|
Antigenic C1-Inhibitor Level
|
Functional C1-Inhibitor Level
|
C1q Level
|
C3 Level
|
|
Hereditary angioedema
|
Recurrent angioedema and abdominal attacks without urticaria; attacks are episodic,
with intervals between periods of swelling; onset in childhood or young adulthood,
with worsening around the time of puberty; prolonged attacks (typically 72–96 h
in duration); family history in 75% of patients; attacks do not respond to antihistamines
or corticosteroids
|
|
(in type I)
or
(in type II)
|
|
|
|
|
Acquired C1-inhibitor deficiency
|
Attacks similar to those in hereditary angioedema; onset in middle age or later;
absence of family history; attacks do not respond to antihistamines or corticosteroids
|
|
or
|
|
|
or
|
|
Inherited angioedema with normal C1-inhibitor levels
|
Family history of angioedema; possible preponderance of women among affected persons;
may be estrogen-dependent; typically manifested after childhood; face, tongue, and
extremities affected more than abdomen; attacks do not respond to antihistamines
or corticosteroids
|
|
|
|
|
|
Caution: Not all labs are able to measure functional C1-INH accurately, and the
sample should be processed within 48 hours. If HAE is suspected, use a laboratory
that can measure this level effectively, and follow up by having the diagnosis confirmed
by a clinical immunologist. 10