Hereditary angioedema (C1 Esterase Deficiency)

Learning objectives

Angioedema:

Angioedema is painless swelling of subcutaneous or submucosal tissues in any part of the body due to increased vascular permeability
Can cause symptoms secondary to a pressure effect on neighboring structures
It can lead to life-threatening complications when occurring in the airway
C1 esterase inhibitor deficiency can be hereditary or acquired, and these two entities are indistinguishable

Hereditary C1 esterase inhibitor deficiency (HAE):

The prevalence of HAE is 1:50000
Either due to:
- Impaired production of C1 esterase inhibitor (type 1, 85% of cases)
- Poor function of the protein (type 2, 15% of cases)
C1 esterase inhibitor (C1-INH) prevents the autoactivation of C1, the first factor of the classical pathway in the complement system
The lack of C1-INH leads to uncontrolled complement activation with the release of vasoactive and chemotactic peptides
Thereby causing increased vascular permeability, vasodilatation, and contraction of the vascular smooth muscle
And resulting in acute, localized, non-pitting, nonpruritic, non-erythematous, and demarcated angioedema
Swelling typically lasts for 2–5 days before resolving spontaneously
The first attack occurs often before the age of 15 and the condition lasts lifelong but symptoms tend to decrease with increasing age
Attacks can be precipitated by a variety of triggers:
- Dental treatment
- Surgery
- Trauma
- Stress (mental or physical)
- Exercise
- Infection
- Alcohol consumption
- Anesthesia
- Menstruation
- Certain agents: ACE-inhibitors and estrogens

Potential airway compromise
Symptoms of acute bowel obstruction: vomiting, anorexia, and severe abdominal pain
Swollen lips, eyelids, tongue, extremities, and genitals