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Lupus Band Test — SCE Rheumatology MCQ

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HardAutoimmune SerologyLupus Band TestSCE Rheumatology

A 30-year-old woman is undergoing investigation for suspected systemic lupus erythematosus. Direct immunofluorescence of clinically normal, sun-protected buttock skin shows a continuous granular band of IgG, IgM and C3 along the dermal–epidermal junction. There is no vessel-wall deposition or epidermal nuclear staining. Which interpretation is most accurate?

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Correct answer: C — A positive lupus band test, providing supportive but non-diagnostic evidence for SLE

This is a positive lupus band test: direct immunofluorescence shows a continuous granular band of immunoglobulins and complement at the dermal–epidermal junction. Detection in clinically uninvolved, sun-protected skin can support SLE, but the test has variable sensitivity and specificity and is not diagnostic in isolation; it must be interpreted with clinical and serological findings. An in-vivo ANA pattern would produce nuclear staining of epidermal keratinocytes. Cytoid bodies are discrete apoptotic keratinocyte remnants rather than a continuous junctional band. Leucocytoclastic vasculitis produces immunoreactant deposition in superficial dermal vessel walls. Weak or interrupted isolated staining may be non-specific, but a continuous granular band containing multiple immunoreactants is not an expected physiological finding in sun-protected skin.

Reference: Ní Maolcatha S, et al. The lupus band test: A review of the sensitivity and specificity in the diagnosis of lupus erythematosus. Skin Health and Disease. 2023;3:e205. https://pubmed.ncbi.nlm.nih.gov/37538339/