Urticaria and Angioedema: Understanding Etiology and Pathogenesis

Introduction

Angioedema is a condition characterized by swelling beneath the skin or mucosal surfaces, often accompanied by urticaria (hives). It can be life-threatening if it affects the airway.

Etiology of Angioedema

1. Immunologic Causes

Angioedema can occur due to hypersensitivity reactions involving histamine release, commonly triggered by allergens.

2. Non-Immunologic Causes

Non-immunologic angioedema results from bradykinin accumulation, often due to ACE inhibitor therapy.

3. Hereditary Angioedema (HAE)

HAE is linked to a deficiency or dysfunction of the C1 esterase inhibitor, leading to excessive bradykinin formation.

Pathogenesis of Angioedema

The underlying mechanisms involve either histamine-mediated increased vascular permeability or bradykinin-induced vasodilation.

1. Histamine-Mediated Pathogenesis

Histamine release from mast cells and basophils causes endothelial gaps to widen, leading to fluid accumulation.

2. Bradykinin-Mediated Pathogenesis

Bradykinin triggers vasodilation, fluid leakage, and reduced degradation due to C1 inhibitor dysfunction.

Clinical Presentation

• Localized swelling affecting lips, eyes, and throat
• Non-pruritic skin involvement
• Severe cases may cause airway obstruction

Conclusion

Angioedema can arise from immunologic or non-immunologic pathways. Early recognition and treatment are crucial in preventing life-threatening complications.