Chronic Spontaneous Urticaria

• By definition, signs and symptoms persist >6 weeks.
• Individual lesions last less than 24 hours, which helps rule out urticarial vasculitis, where lesions typically persist longer and may leave residual marks.
• Rash/lesions resolve without residual pigmentation or bruising.
• There is no consistent pattern of triggers, making this not inducible (unlike physical or inducible urticarias, e.g. dermographism, cholinergic urticaria)

Incorrect Answers:

Atopic Dermatitis

1. Typically chronic, beginning in childhood, with relapsing/remitting course.
2. Distribution is usually flexural (antecubital/popliteal fossae) in older children/adults, not widespread acute onset.
3. Associated features: secondary changes including xerosis, lichenification; personal/family history of atopy (here, only asthma is mentioned but no long-standing dermatitis).
4. The acute migratory nature of this rash argues against atopic dermatitis.

Prurigo Nodularis

1. Characterized by chronic, firm, hyperkeratotic nodules due to persistent scratching.
2. Develops over weeks to months, not acutely overnight. Diagnostic criteria require at least 6 weeks of activity to be considered.
3. Lesions are localized, constant, and persistent, unlike urticaria.
4. The patient’s rash is fleeting and widespread, not consistent with nodular prurigo.

Scabies Infestation

• Presents with burrows, papules, and intense nocturnal pruritus.
• Classic distribution: interdigital webs, wrists, waistline, genitalia.
• Scabies lesions are persistent, not transient or migratory.
• No mention of close contact with similar symptoms

Acute Urticaria

• Key features:
  • Sudden onset of pruritic eruption
  • Transient lesions: dermal, edematous plaques with no surface change (i.e. scale) appear in different locations at different times.
  • Associated angioedema: lip swelling.
  • No chronicity: duration < 6 weeks.

• These points strongly indicate acute urticaria, which is characterized by itchy wheals (hives) that appear and resolve within hours, with the entire episode lasting less than 6 weeks. It is often triggered by infection, medication, food, or occasionally remains idiopathi