Sneddon Syndrome — SCE Dermatology MCQ

Correct answer: D — Sneddon syndrome (livedo racemosa + cerebrovascular disease without APS antibodies)

The correct answer is D, Sneddon syndrome (livedo racemosa plus cerebrovascular disease without APS antibodies). This patient has the classic diagnostic triad: persistent livedo racemosa, recurrent small deep cerebral infarcts, and a skin biopsy showing non-inflammatory thrombotic vasculopathy of dermal vessels, with negative antiphospholipid antibodies. Sneddon syndrome is defined precisely by this combination, and diagnosis is supported by livedo racemosa with characteristic biopsy findings and focal neurological deficits or imaging evidence of stroke. The absence of vessel wall inflammation on histology excludes a vasculitic process, while the negative antiphospholipid screen is a defining feature separating primary Sneddon syndrome from antiphospholipid-associated disease. Why the other options are wrong: B. Cholesterol embolisation: causes livedo reticularis/racemosa and infarcts via atheroembolic showering, typically after vascular intervention, with biopsy showing cholesterol clefts within occluded vessels, not a non-inflammatory thrombotic vasculopathy. E. Antiphospholipid syndrome: requires persistently positive antiphospholipid antibodies (lupus anticoagulant, anticardiolipin, or anti-beta2-glycoprotein I) alongside thrombosis; this patient has tested negative, excluding APS by definition. C. Vasculitis: skin biopsy in vasculitis shows inflammatory infiltrate within or around vessel walls (leucocytoclasis, fibrinoid necrosis), which is explicitly absent here as the pathology is non-inflammatory. A. Atherosclerosis: produces large-vessel occlusive disease and territorial infarcts from plaque, not the small dermal vessel non-inflammatory thrombosis or livedo racemosa pattern described. Key point: Sneddon syndrome is diagnosed by the triad of livedo racemosa, cerebrovascular disease, and antiphospholipid-antibody-negative non-inflammatory thrombotic vasculopathy on deep skin biopsy.

Reference: DermNet NZ, Sneddon Syndrome, https://dermnetnz.org/topics/sneddon-syndrome