Angioedema
Angioedema is characterized by deep dermal and subcutaneous tissue swelling. Unlike urticaria (which is superficial/epidermal), angioedema is non-pitting and can involve the mucous membranes, posing a life-threatening risk of airway obstruction.
Primary Etiological Categories
| Type | Mediator | Key Triggers |
|---|---|---|
| Histaminergic | Histamine | Allergens, food, and drugs (often associated with hives). |
| Bradykinin-mediated | Bradykinin | ACE Inhibitors, Hereditary Angioedema (C1-esterase deficiency). |
Clinical Management Pearl
- ACE Inhibitors: A classic cause. The swelling can occur even years after starting the drug. Discontinuation is the priority.
- Hereditary Angioedema (HAE): Characterized by recurrent episodes of swelling without urticaria or pruritus. Often triggered by trauma or dental procedures.
- Airway Management: If laryngeal edema is suspected, early intubation is life-saving. Epinephrine is effective for histamine-mediated cases but is often ineffective for bradykinin-mediated cases (like ACE-inhibitor or HAE-induced).
High-Yield Exam Pearl:
- Distinction: Urticaria (itchy, superficial, hives) vs. Angioedema (painless, deep, swelling).
- HAE Diagnosis: Look for low levels of C4 (screening test) and quantitative/functional deficiency of C1-esterase inhibitor.