A skin biopsy shows basket-weave hyperkeratosis, hypergranulosis, and irregular acanthosis without parakeratosis. The rete ridges show a 'saw-tooth' appearance. There is a band-like lymphocytic infiltrate at the dermoepidermal junction with vacuolar change at the basal layer. Occasional civatte bodies (colloid bodies) are noted. DIF shows fibrinogen at the BMZ in a shaggy pattern. What is the diagnosis?
- A Lupus erythematosus
- B Psoriasis
- C Lichen planus ✓
- D Pityriasis rosea
Correct answer: C. Lichen planus
Explanation
This is the classic histopathology of lichen planus: wedge-shaped hypergranulosis, saw-tooth rete ridges, band-like lichenoid lymphocytic infiltrate at the DEJ, vacuolar change (interface dermatitis), and civatte/colloid bodies (apoptotic keratinocytes). DIF in LP characteristically shows shaggy/fibrillar fibrinogen deposits at the BMZ, distinguishing it from lupus (lupus band with IgG/IgM/C3 at BMZ). Psoriasis shows Munro microabscesses and suprapapillary thinning without interface change.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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