Angioedema

Basics

Description

  • Nonpruritic, well-demarcated, nonpitting edema of the dermis
  • Due to the release of inflammatory mediators that cause dilation and increased permeability of capillaries and venules:
    • Mast cell mediated
    • Kinin related from the generation of bradykinin and complement-derived mediators
  • Similar in pathologic basis to urticaria except that affected tissue lies deeper:
    • Urticaria affects superficial tissue and causes irritation to mast cells and nerves in the epidermis leading to intense itching
    • Angioedema occurs in deeper layers, which have fewer mast cells and nerves, therefore causing less itching
    • Angioedema can affect tissues other than the skin, e.g., the gut
    • Angioedema may be seen in a mixed picture along with urticaria
  • Hereditary and acquired etiologies are due to deficiencies in the quantity and/or function of C1-INH rather than classic Gell–Coombs immediate hypersensitivity-type reactions
  • Hereditary angioedema (HAE):
    • An autosomal dominant disorder caused by a deficiency of C1-INH
    • The prevalence of HAE is estimated to range from 1:30,000–1:80,000
    • C1-INH has a regulatory role in the contact, fibrinolytic, and coagulation pathways
    • Deficiency results in unregulated activity of the vasoactive mediators bradykinin, kallikrein, and plasmin
    • More than 100 mutations of the C1-INH gene have been reported
    • Type 1 (85% of cases): Decreased expression of C1-INH
    • Type 2 (15% of cases): Normal plasma levels of C1-INH but the protein is dysfunctional
    • Type 3 (very rare): Mutation in coagulation factor XII resulting in increased kinin production:
  • Symptoms increased by estrogen-containing medications
    • Episodes occur in all 3 types when inflammation, trauma, or other factors lead to depletion of C1-INH
  • Acquired angioedema:
    • Normal quantities and function of C1-INH
    • Type 1 is associated with lymphoproliferative diseases and caused by consumption of the C1-INH protein by malignant cells
    • Type 2 is autoimmune caused by circulating antibodies that inactivate C1-INH
  • ACE inhibitor–induced angioedema:
    • Accounts for 20–30% of all angioedema cases presenting to ER reported in 0.1–0.7% of patients taking ACE inhibitors
    • Usually occurs during the first month of taking the medication; however, the first event may occur spontaneously after many years
    • African Americans are at a higher risk of experiencing ACE inhibitor–induced angioedema than whites

Etiology

  • Critical point: Your history and exam should direct you to suspect EITHER a bradykinin-mediated OR a histamine-mediated etiology for the patient's angioedema attack. This is important in choosing therapies which are effective against the targeted mediator
  • Kinin-related etiologies:
    • HAE
    • Acquired angioedema:
      • Lymphoproliferative
      • Autoimmune
    • ACE inhibitor–induced
  • Mast cell–mediated etiologies:
    • Food allergies:
      • Nuts
      • Eggs/milk
      • Shellfish
      • Soy/wheat
    • Drug allergies:
      • Aspirin
      • NSAID
      • Antihypertensives
      • Narcotics
      • Oral contraceptives
    • Insect stings
    • Physically induced:
      • Cold/heat
      • Exercise/trauma/vibrations
      • Stress
      • UV light
  • Hypereosinophilic syndromes such as Gleich syndrome (rare)
  • Thyroid autoimmune disease
  • Idiopathic recurrent AE

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