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urticaria
URTICARIA
Urticaria is characterized by sudden appearance of wheals and/or angioedema.
The intensity of the pruritus varies but may be severe enough to disrupt sleep, work or school.
It is classified acute if the urticaria has been present for <6 weeks and chronic if >6 weeks. A specific cause is more likely to be identified in acute cases.
It can be triggered by immunological or nonimmunological mechanism.

Diagnosis

  • Diagnosis is based on patient’s history & physical exam

Classification

  • Urticaria is classified as acute or chronic
    • A specific cause is more likely to be identified in acute cases
  • Can be triggered by immunological or non-immunological mechanism

Acute Urticaria

  • Lesions occurring <6 wk in duration & usually w/o angioedema
  • More common in children & young adults & tends to have a triggering event

Chronic Urticaria

  • More common in adults (3rd & 4th decades of life), symptoms last >6 wk

Chronic Spontaneous Urticaria

  • Urticaria that has spontaneously recurred at least 2x/wk for >6 wk w/ unknown causes

Inducible Urticaria

  • Cold contact
  • Delayed pressure
  • Heat contact
  • Symptomatic dermographism
    • Daily lesions & recurrent episodic lesions are not differentiated
  • Solar urticaria
  • Vibratory angioedema
  • Aquagenic urticaria
  • Cholinergic urticaria
  • Contact urticaria

Autoimmune Chronic Spontaneous Urticaria (ACU)

  • Proposed gold standard for diagnosis of ACU (combination of all 3 parameters):
    • Positive bioassay [eg basophil histamine release assay (BHRA), basophil activation marker expression] AND
    • Positive autoreactivity [eg positive autologous serum skin test (ASST)] AND
    • Positive immunoassay for specific IgG autoantibodies against FcεRIα and/or anti-IgE

Physical Examination

Look for typical lesions of urticaria

  • Wheals which typically are fleeting, lasting w/in 1-24 hr, have a central swelling of variable size surrounded by erythema & associated w/ itching, sometimes burning sensation
  • Angioedema characterized by a sudden evident swelling of the lower dermis & subcutis which may last up to 72 hr
  • Lesions may appear on any part of the body

Stroke the arm to test for dermographism/dermatographism

  • Discontinue antihistamine therapy for at least 2-3 days, immunosuppressive therapy for at least a wk
RECOMMENDED DIAGNOSTIC TESTS FOR URTICARIA SUBTYPES
Subtype Test Extended Diagnostic Tests
Acute spontaneous Presence of wheals/pruritus None
Chronic idiopathic spontaneous Differential blood count & ESR or C-reactive protein (CRP), omission of suspected drugs (NSAIDs, ACE inhibitors, antibiotics) Test for: Infectious diseases, type 1 allergy, autoantibodies, thyroid hormones, skin test, pseudoallergen-free diet for 3 wk, lesional skin biopsy*, autologous serum skin test
Autoimmune chronic spontaneous Autoreactivity, functional bioassay & immunoassay Differential blood count, ESR/CRP cryoproteins
Cold contact Cold provocation & threshold test (eg ice cubes, cold water) Differential blood count, ESR/CRP cryoproteins, rule out other diseases/infections
Delayed pressure Pressure test (0.2-1.5 kg/cm2 for 10 & 20 min) & threshold test None
Heat contact Heat provocation & threshold test (eg warm water) None
Solar UV & visible light of different wavelengths Rule out other light-induced dermatoses
Demographic Test by stroking the arm Differential blood count, ESR/CRP cryoproteins
Aquagenic Apply wet cloths set at body temperature for 20 min None
Cholinergic Exercise & hot bath provocation None
Contact Cutaneous provocation test, prick/patch test (see results after 20 min) None
Exercise-induced History of urticaria after exercise, appearing w/ or w/o food intake but not after a hot bath None
Modified from: EAACI/GA2LEN/EDF/WAO guidelines: management of urticaria, 2013.
*Lesional skin biopsy indicated for lesions lasting for >36 hr

Assess disease activity of chronic spontaneous urticaria

  • Several guidelines recommend using the Urticaria Activity Score (UAS7) system in assessing disease severity
    • Summation of scores of symptoms during a 7-day period
  • 1 = mild wheals (<20 wheals w/in 24 hr) + mild (nontroublesome) pruritus
  • 2 = moderate wheals (20-50 wheals w/in 24 hr) + moderate (troublesome but does not interfere w/ daily activities or sleep) pruritus
  • 3 = intense wheals (>50 wheals w/in 24 hr or large confluent wheals) + intense (severely troublesome, interferes w/ daily activities & sleep) pruritus
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