Urticarial vasculitis — SCE Rheumatology MCQ

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ModerateVasculitisUrticarial vasculitisSCE Rheumatology

A 45-year-old woman has recurrent urticarial plaques lasting more than 24 hours and leaving bruised pigmentation. She has arthralgia and low C1q with low C4. Skin biopsy shows leukocytoclastic vasculitis. ANA is negative and there is no renal disease. What is the most likely diagnosis?

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Correct answer: C — Hypocomplementaemic urticarial vasculitis

Explanation lettering: D = shown as B · E = shown as C · C = shown as D · B = shown as E

Hypocomplementaemic urticarial vasculitis is best because urticarial lesions lasting over 24 hours with residual bruising, low complement and leukocytoclastic vasculitis indicate hypocomplementaemic urticarial vasculitis. A is less suitable because mastocytosis causes pigmentary lesions and mediator symptoms rather than vasculitic biopsy; B is less suitable because chronic urticaria lesions usually resolve within 24 hours without bruising or vasculitis; C is less suitable because cutaneous lupus would have lupus-specific rash and serology/histology; D is less suitable because serum sickness may be acute after exposure but does not explain recurrent low-C1q disease. Clinical pearl: duration of individual wheals is a useful discriminator between urticaria and urticarial vasculitis.

Reference: Oxford Textbook of Rheumatology