Cutaneous small-vessel vasculitis — SCE Rheumatology MCQ

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ModerateVasculitisCutaneous small-vessel vasculitisSCE Rheumatology

A 43-year-old woman develops palpable purpura on both lower legs after starting a new antibiotic. She is afebrile and has ankle arthralgia. Urinalysis is normal and creatinine is normal. The rash is 36 hours old and the clinician wants diagnostic confirmation. What is the most appropriate investigation?

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Correct answer: B — Skin biopsy including direct immunofluorescence

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

Skin biopsy including direct immunofluorescence is best because early skin biopsy with immunofluorescence can confirm leukocytoclastic vasculitis and help identify immune-complex deposition. A is less suitable because Schirmer test evaluates ocular dryness in Sjögren disease; B is less suitable because renal angiography is not appropriate without renal or medium-vessel features; D is less suitable because temporal artery biopsy is for suspected GCA; E is less suitable because dual-energy CT assesses urate deposition. Clinical pearl: biopsy yield is highest from a fresh lesion, ideally within 24–48 hours.

Reference: Oxford Textbook of Rheumatology; EULAR vasculitis recommendations