A skin biopsy of a patch of erythema shows deep periadnexal and perivascular lymphocytic infiltrate extending into the reticular dermis, follicular plugging, basement membrane thickening on PAS stain, and mucin deposition. DIF shows granular IgM and C3 at the dermoepidermal junction. The diagnosis is:

• A Discoid lupus erythematosus ✓
• B Cutaneous lichen planus
• C Lymphocytic infiltrate of Jessner
• D Granuloma annulare

Explanation

Discoid lupus erythematosus (DLE) histologically shows follicular plugging, liquefactive degeneration of basal keratinocytes, thickening of the PAS-positive BMZ, perivascular and periadnexal lymphocytic infiltrate extending into the deep reticular dermis, and dermal mucin deposition. DIF of lesional skin shows granular IgM, IgG, and C3 at the DEJ (positive 'lupus band test' in lesional skin). Jessner's lymphocytic infiltrate lacks BMZ changes and DIF deposits. Granuloma annulare shows palisaded histiocytes with mucin.

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.