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Board Review

Intussusception Caused by Hereditary Angioedema?

Q.  A young female patient of mine, with a family history of Type 3 hereditary angioedema (HAE) in her mother and maternal grandfather, was in the emergency department recently with severe abdominal pain and vomiting.  On ultrasound she had an intussusception and there was also some discussion about whether her appendix was “borderline” – depends on whether you ask the pediatric radiologist or the surgeon.  The intussusception was midline, inferior to her umbilicus.  She started feeling better because the intussusception apparently resolved without further intervention.  A couple weeks later, she had a repeat episode of abdominal pain and nausea, no vomiting, with the pain less severe.  Again, this resolved spontaneously, this time while she was still waiting in the emergency department. for evaluation.  In the past, she has had normal qualitative and functional C1 esterase inhibitor assays.  Please comment on the likelihood of focal edema in small bowel causing an intussusception, and this being HAE in origin.  Of note, the patient has also been seen several times for what seems to be a parotid duct infection or stone along her right cheek, which has never looked like angioedema of the cheek, clinically.

Pertinent laboratory values include an elevated WBC of 16.9k/uL (neutrophilia of 11.9k/uL  and slight monocytosis) from her recent episode, normal C4, and normal repeat C1 esterase inhibitor levels.

A. Intussusception has certainly been reported in HAE.  In some cases, the swollen bowel is pulled into the normal bowel.  In cases of intussusception caused by HAE, treatment reduces the swelling and the intussusception reverses, without need for surgery.  Confounding the situation, the WBC usually is elevated in HAE abdominal attacks.  This often leads the ED physician and the surgeon to believe it is an acute abdomen and thus perform surgery.  (Hopefully a CT scan is done first.)  In a patient with HAE who presents with abdominal pain, a trial of one the medications approved for “on demand therapy” should be tried before other interventions.  Usually within an hour a patient will be improved and it will be apparent that neither a CT scan nor surgery are necessary.  If symptoms fail to resolve, then further appropriate workup is necessary.

The most important aspect of this case is the family history.  HAE type 1, 2 and 3 (this terminology is soon to change) appear clinically identical with only minor differences.  The gene area for type 1 and 2 is very unstable and predisposed to mutation and thus 25% of type 1 and 2 patients have new mutations and no family history of HAE.  This is not the case with HAE type 3.  The chromosome area thought to be responsible for type 3 HAE is very stable and not subject to a high rate of mutations.  For this reason we usually insist on a family history to make the diagnosis of type 3 HAE. This is especially true since there are no diagnostic tests for HAE type 3. In type 1 and 2 the best screening test is C4, but this test is normal in HAE type 3.   In type 1 HAE the protein,  C1 esterase inhibitor, does not fold correctly, not secreted for this reason, and thus the protein is low and the function of the protein is low.  In type 2 the protein is secreted from cells since it folds correctly, but the active part of the protein is dysfunctional and thus the protein may be normal or even high, but the function is compromised.  In type 3 both the protein and the protein’s function are normal, again making it difficult to diagnose.  There is an association of type 3 and “gain of function of Factor 12”, but this is neither sensitive nor specific for type 3 HAE.  Presently, we are desperate for a diagnostic test for this disorder, especially since it appears that this diagnosis is often given inappropriately to patients.  Lastly, the same therapies for type 1 and 2 may be effective for type 3, but the data are poor and limited and until we have a diagnostic test it will be impossible to perform good trials to properly assess therapies for this disorder.

Importantly, in my experience at our institution, first attacks in children are often abdominal and have led to removal of normal organs such as the appendix.  For this reason we screen for HAE early in life and if the patient has the disease we prescribe therapy to have on hand to treat attacks even if attacks have not yet started.  This way if abdominal pain occurs the patient can be treated to see if it is HAE and within hour or so symptoms should start to decrease and this would suggest HAE.  If symptoms persist or worsen then further intervention is necessary.  Hopefully this approach will reduce unnecessary surgery and irradiation.  Of note, the recurrent parotid duct infection or stone is unlikely part of her HAE. 

 
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