Angioedema
Basics
Basics
Basics
Description
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
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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