A 30-year-old woman with cutaneous lupus shows the 'lupus band' on DIF of non-sun-exposed normal skin. This finding indicates:
- A Discoid lupus erythematosus with localized disease
- B Subacute cutaneous LE — always shows positive lupus band in normal skin
- C Systemic lupus erythematosus — positive lupus band in non-sun-exposed normal skin suggests systemic disease ✓
- D Drug-induced lupus — characteristic finding in normal skin
Correct answer: C. Systemic lupus erythematosus — positive lupus band in non-sun-exposed normal skin suggests systemic disease
Explanation
The lupus band test (LBT) — DIF showing immunoglobulin (IgG, IgM, IgA) and/or C3 deposits at the dermoepidermal junction — is positive in lesional skin in all forms of lupus. However, when positive in NON-LESIONAL, non-sun-exposed skin (e.g., inner forearm), it is specific for SLE (systemic disease) and correlates with disease activity, particularly nephritis. Discoid LE shows positive LBT only in lesional skin. SCLE shows positive LBT in lesional skin but typically not in non-exposed normal skin.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
Written and medically reviewed by the StethoPrep medical team.