A 40-year-old woman presents with recurrent wheal-like eruptions on the trunk that are painful rather than itchy, last more than 24 hours, and leave bruise-like discolouration. Biopsy shows a leukocytoclastic vasculitis. Which laboratory finding would support the hypocomplementaemic form of this condition?

• A Elevated serum IgE level
• B Positive antiphospholipid antibody titre
• C Peripheral blood eosinophilia
• D Low serum C3 and C4 levels ✓

Explanation

Urticarial vasculitis differs from ordinary urticaria because individual lesions persist beyond 24 hours, are painful or burning, and heal with purpuric staining. The hypocomplementaemic subtype shows depressed C3 and C4, may be associated with connective tissue disease or viral infection, and carries a higher risk of systemic involvement such as glomerulonephritis, arthralgia, and abdominal pain. Elevated IgE points toward atopic ordinary urticaria, and eosinophilia suggests a drug reaction or bullous pemphigoid rather than this entity.

Reference: Bolognia, Schaffer and Cerroni, Dermatology, 5th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.