Diagnosis

Urticaria

Etiology

Cause [cnj]

1. Physical: cold, solar, heat, pressure, cholinergic (anxiety, sexual excitement, exercise)

2. Hypersensitivity: Ingestion, Inhalation, Instillation, Injection, Insertion, Insect bites, Infestation, Infection, Infusion, Inunction

3. Autoimmune

4. Pharmacological: Aspirin, NSAIDs, ACE inhibitor, morphine

5. Contact: Latex

6. Endogenous causes:

   • Viral (Hepatitis, EBV, HIV)

   • Bacterial

   • Mycoplasma

   • Intestinal parasites

   • Connective tissue disorder

   • Hypereosinophilic syndrome

   • Hyperthyroidism

   • Cancer

7. Exogenous causes:

   • Drugs (topical and systemic)

   • Perservatives in lotion

   • Foods

   • Insect bites/venoms

   • Inhalants

   • Pollens

Pathophysiology [wnn]

1. Increase circulating levels of inflammatory cytokines and histamine-releasing factors:

   • Chronic infection

   • Allergens

   • Drugs

2. Mast/basophil cell degranulation --> histamine, cytokines, and chemokines

   • Immunologic trigger: IgE

   • Nonimmunologic triggers: Pressure, vibration, temperature changes, sunlight

3. Vasodilation and increased capillary permeability --> wheals and angioedema

4. Clinical presentation:

   • Pruritic pink-to-red papules or plaques

   • Resolve within 24 hours without residual discoloration

Complications

• Anaphylaxis

• Edema of the larynx -> asphyxiation

Epidemiology

Incidence per 100.000 [qq3][q4d][64m][4uq][wsv][ycu]

Approach

• Dermatoscopy: blanching, raised, palpable wheals often separated by normal skin, but may coalesce rapidly to form large areas of erythematous, raised lesions that blanch with pressure.

• Blood test if recurrent urticaria: CBC, erythrocyte sedimentation rate, CRP, TSH, metabolic panel (liver, kidney), blood culture [tww]

• Serelogy: total IgA levels, thyroid auto-antibodies, anti-nuclear antibody level (ANA), Anti–Sjögren-syndrome-related antibody, Anti-citrullinated peptide antibody, Anti-tissue transglutaminase antibody, Rheumatoid factor, complement levels (C3, C4), Hepatitis serology, H pylori stool antigen testing, Serum protein electrophoresis [wnn]

• Allergy testing: radioallergosorbent, scratch, patch test, prick test, dimethylsulfoxide (DMSO) test

• Stool studies for ova and parasites

Treatment

1. Prophylaxis: [mp4][tww]

   • Avoid any known medication, food, or other allergen

   • Protective gear: gloves, mask, creams or emollients

2. Antihistamine: [mp4][wnn]

   • 1st line: cetirizine, loratadine, fexofenadine, desloratadine

   • 2nd line: famotidine or cimetidine

3. Monoclonal antibody: Omalizumab has a high affinity for free IgE [wnn]

4. Immunosuppresion: Ultraviolet A and B light, Aspirin, NSAIDs, cyclosporine, methotrexate [tww]

5. Prednisone 40–60 mg/day for 5 days in adults or 1 mg/kg/day for 5 days in children

6. Subcutaneous epinephrine

Differential diagnoses

Anaphylaxis, Angioedema, Bullous pemphigoid, Contact dermatitis, Cryoglobulinemia, Dermatitis herpetiformis, Dermatographism, Drug eruptions, Eczema, Erysipelas, Erythema multiforme, Hypereosinophilic syndrome, Mastocytosis, Pemphigoid gestationis, Scabies, Still disease, Urticarial vasculitis, Wells' syndrome