Urticaria and Angioedema

Urticaria & Angioedema - Defining the Duo

• Urticaria (Hives)

  • Superficial dermal edema presenting as wheals.
  • Intensely pruritic, erythematous, circumscribed, raised, blanching plaques.
  • Individual lesions transient, lasting < 24 hours.
  • No post-inflammatory changes.

• Angioedema

  • Deeper edema: dermis, subcutaneous tissue, or submucosa.
  • Common sites: face, lips, tongue, larynx, extremities, genitalia.
  • Often painful or burning; pruritus usually absent or mild.
  • Slower onset; resolves over 24-72 hours.
  • Laryngeal involvement can be life-threatening.

• Urticaria & Angioedema often coexist (40-50%); angioedema alone (10%), urticaria alone (~40-50%).

⭐ Hereditary Angioedema (HAE) is often associated with C1 esterase inhibitor deficiency/dysfunction and does NOT typically present with urticaria or pruritus.

Mechanisms & Categories - How & What Type

• Mechanisms:
  • Histaminergic: Mast cell degranulation (Histamine, Prostaglandins, Leukotrienes) → Urticaria (wheals) & some Angioedema. Typically pruritic.
  • Bradykininergic: ↑ Bradykinin (e.g., due to C1-INH deficiency or ACE inhibitors) → Angioedema (deeper swelling). Typically non-pruritic, no wheals.
• Urticaria Types:
  • Acute: < 6 weeks duration.
  • Chronic: > 6 weeks duration.
    • Chronic Spontaneous Urticaria (CSU).
    • Chronic Inducible Urticaria (CIndU) - e.g., symptomatic dermographism, cold urticaria, cholinergic urticaria.
• Angioedema (AE) Types:
  • With Urticaria (Histaminergic): Allergic, idiopathic spontaneous, secondary to CIndU.
  • Without Urticaria (Primarily Bradykininergic):
    • Hereditary Angioedema (HAE): C1-INH deficiency (Type I) or dysfunction (Type II), or HAE with normal C1-INH.
    • Acquired Angioedema (AAE): C1-INH deficiency.
    • ACE Inhibitor-induced Angioedema.
    • Idiopathic Non-Histaminergic Angioedema.

⭐ Hereditary Angioedema (HAE) Type I is characterized by low C1-INH levels and function, while HAE Type II has normal (or elevated) C1-INH levels but impaired function. Both result in unregulated bradykinin production during attacks.

Causes & Child Triggers - The Usual Suspects

• Infections (Key trigger in children):
  • Viral (URI), bacterial (Strep, Mycoplasma), parasitic.
• Food Allergens:
  • Milk, egg, peanut, tree nuts, soy, wheat, fish, shellfish.
  • Food additives (rare: benzoates, tartrazine).
• Drugs:
  • Antibiotics (β-lactams, sulfonamides), NSAIDs.
  • Opiates, radiocontrast (non-allergic histamine release).
• Physical Urticarias:
  • Dermatographism (commonest), cold, cholinergic (heat/exercise), solar, pressure.
• Insect Bites/Stings:
  • Bees, wasps, ants, mosquitoes.
• Contact/Inhalants:
  • Latex, dander, pollen, dust mites.
• Idiopathic: Common, especially chronic cases.

⭐ Infections are the primary trigger for acute urticaria in children.

Workup & Treatment - Solving & Soothing

• Workup: Identify triggers; differentiate acute (<6 wks) vs. chronic (>6 wks).
  • Acute: Clinical diagnosis. Tests if recurrent/severe.
  • Chronic (CSU): CBC, ESR/CRP. Consider thyroid Abs, specific IgE.
  • Angioedema (no wheals): C4, C1-INH level & function (HAE screen).

• Treatment:
  • Avoid triggers. H1-antihistamines (2nd gen preferred, e.g., Cetirizine) are mainstay.
  • CSU: Step-up H1 dose (up to 4x), then Omalizumab, then Cyclosporine.
  • Severe Acute: Short course OCS (Prednisolone 0.5-1 mg/kg/day, 3-7 days). Epinephrine if anaphylaxis.
  • HAE: Acute (C1-INH concentrate, Icatibant); Prophylaxis (C1-INH, Lanadelumab). FFP if others unavailable.

⭐ Omalizumab, an anti-IgE monoclonal antibody, is a key treatment for refractory chronic spontaneous urticaria not responding to high-dose antihistamines.

High‑Yield Points - ⚡ Biggest Takeaways

• Urticaria: transient, pruritic wheals. Angioedema: deeper, non-pruritic swelling; laryngeal involvement is critical.
• Differentiate acute (<6 weeks) from chronic (>6 weeks) urticaria.
• Key mechanism: mast cell degranulation releasing histamine.
• First-line: second-generation H1 antihistamines for symptomatic relief.
• Hereditary Angioedema (HAE): bradykinin-mediated, C1-inhibitor deficient; antihistamines/steroids are ineffective.
• Common triggers: infections, drugs (NSAIDs, antibiotics), foods.
• In anaphylaxis with urticaria/angioedema, epinephrine is life-saving.