Hereditary angioedema

Definition

• Congenital defect in C1 inhibitor (or C1 esterase inhibitor) causing recurrent episodes of angioedema potentially involving any mucosal surface

Classification

• Type I: abnormally low levels of normal serum C1 inhibitor
• Type II: normal levels of abnormal serum C1 inhibitor
• Type III: increased kininogenase activity (C1 inhibitor is normal)

Epidemiology

• 25% of cases are caused by do novo mutations

Clinical Manifestations

• Recurrent episodes of angioedema (can involve any mucosal surface) without urticaria or pruritis
• May have a family history

Investigations

• Screening bloodwork in suspected cases:
  • Complement component 4 (C4), which may be low
  • C1 inhibitor (C1INH) antigenic levels
  • C1INH functional levels

Management

• Acute
• Chronic

Further Reading

• Betschel S, et al. Canadian hereditary angioedema guideline. Allergy Asthma Clin Immunol. 2014;10(1):50.
• Cicardi M, et al. Classification, diagnosis, and approach to treatment for angioedema: consensus report from the Hereditary Angioedema International Working Group. Allergy. 2014;69(5):602-16.