skip to main content

HUVS — SCE Rheumatology MCQ

Instant feedback + full explanation. One question, done properly.

HardVasculitisHUVSSCE Rheumatology

A 55-year-old woman has an 8-month history of recurrent tender urticarial plaques. Individual lesions persist for 36–72 hours and resolve with residual ecchymotic pigmentation. She also reports intermittent arthralgia and has had one episode of episcleritis. Skin biopsy shows small-vessel leucocytoclastic vasculitis. C1q, C3, C4 and CH50 are reduced, and anti-C1q antibodies are detected. ANA, anti-dsDNA and extractable nuclear antigen antibodies are negative; serum cryoglobulins and immunofixation are also negative. Which diagnosis best accounts for the overall presentation?

Educational content. Not a substitute for clinical judgement or local policy.

Reveal the answer and explanation

Correct answer: A — Hypocomplementaemic urticarial vasculitis (anti-C1q vasculitis)

The diagnosis is hypocomplementaemic urticarial vasculitis, also termed anti-C1q vasculitis. The discriminating combination is persistent bruising wheals, biopsy-proven leucocytoclastic vasculitis, classical-pathway complement consumption—particularly low C1q—and anti-C1q antibodies. Arthralgia and ocular inflammation are recognised systemic manifestations. SLE can overlap with or resemble this disorder, but negative ANA, anti-dsDNA and ENA testing and the absence of other defining lupus features make option B less likely. Normocomplementaemic urticarial vasculitis is excluded by the complement results. Schnitzler syndrome is usually associated with a monoclonal IgM or IgG component and neutrophilic dermatosis rather than leucocytoclastic vasculitis. Negative cryoglobulins and the urticarial anti-C1q phenotype argue against mixed cryoglobulinaemic vasculitis.

Reference: Jachiet M, Flageul B, Bouaziz J-D, et al. Hypocomplementemic urticarial vasculitis. La Revue de Médecine Interne. 2018;39(2):90–98. https://pubmed.ncbi.nlm.nih.gov/28457680/