A 35-year-old woman presents with persistent erythema on the cheeks and nose for 6 months, photosensitivity, oral ulcers, and new-onset arthralgia. ANA is positive (1:320), anti-dsDNA is elevated, and C3/C4 are reduced. Skin biopsy shows interface dermatitis with IgG, IgM, and C3 at the DEJ on DIF (positive lupus band test). The lupus band test in normal sun-exposed skin of SLE patients shows deposits, while in SCLE it is limited to:

• A Both lesional and non-lesional skin in SCLE
• B Non-lesional sun-protected skin in SCLE
• C Lesional skin only in SCLE, with negative lupus band in normal non-lesional sun-exposed skin ✓
• D Negative in all skin sites in SCLE

Explanation

The lupus band test (LBT) is the DIF finding of immunoreactant (IgG, IgM, C3) deposits at the dermoepidermal junction. In SLE: LBT is positive in both lesional and non-lesional sun-exposed skin (and often non-exposed skin) — correlating with systemic disease activity and anti-dsDNA levels. In SCLE (subacute cutaneous lupus): LBT is positive only in lesional skin; non-lesional skin is negative. In DLE (discoid LE): LBT is positive in lesional skin only. This distinction helps differentiate SLE from purely cutaneous forms of lupus.

Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.

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Written and medically reviewed by the StethoPrep medical team.