Which finding on immunofluorescence of a skin biopsy of non-lesional sun-exposed skin is most specific for systemic lupus erythematosus?
- A IgA deposits at the dermoepidermal junction
- B IgG linear deposits at the dermoepidermal junction
- C IgG + IgM + C3 granular deposits at the dermoepidermal junction (positive lupus band test) ✓
- D C3 deposits around dermal vessels
Correct answer: C. IgG + IgM + C3 granular deposits at the dermoepidermal junction (positive lupus band test)
Explanation
The lupus band test (direct immunofluorescence of non-lesional skin) shows granular deposits of IgG, IgM, and/or C3 at the dermoepidermal junction. A positive lupus band on non-sun-exposed, non-lesional skin has ~70% sensitivity and high specificity for SLE. Linear IgG at the BMZ is characteristic of bullous pemphigoid. IgA deposits are seen in dermatitis herpetiformis (DH) and linear IgA disease.
Reference: Harrison's Principles of Internal Medicine, 21st ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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