Microscopic polyangiitis — SCE Rheumatology MCQ

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ModerateVasculitisMicroscopic polyangiitisSCE Rheumatology

A 33-year-old woman has breathlessness, haemoptysis and rapidly worsening renal function. Examination shows purpura and basal crackles are present. Investigations show MPO-ANCA is positive with red-cell casts. The admitting team asks which diagnosis best explains the whole presentation. What is the most likely diagnosis?

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Correct answer: C — Microscopic polyangiitis

Microscopic polyangiitis is the best answer because the pattern described is most consistent with Microscopic polyangiitis, including the distribution of symptoms and the targeted investigation results. Antiphospholipid syndrome is a plausible distractor, but it does not account for the key discriminator in the stem. Paget disease of bone and Polyarteritis nodosa would be more appropriate in a different clinical pattern or at another point in the pathway, while Psoriatic arthritis is suboptimal for this presentation. Clinical pearl: in SCE-style questions, the decisive clue is usually the pattern across joints, extra-articular features and targeted immunology rather than a single antibody result.

Reference: BSR GCA guideline; EULAR ANCA-associated vasculitis recommendations; BNF