A 72-year-old man develops large tense bullae over flexural surfaces and lower abdomen; some arise on erythematous bases. Nikolsky sign is negative. Biopsy shows a subepidermal blister with eosinophils, and direct immunofluorescence reveals linear IgG and C3 along the dermoepidermal junction. The target antigen lies in which structure?

• A Desmosomal cadherins between keratinocytes
• B Keratin 5 intermediate filaments
• C Type IV collagen of the lamina densa
• D Hemidesmosomes anchoring basal keratinocytes to the basement membrane ✓

Explanation

Bullous pemphigoid features autoantibodies against BPAG1 and BPAG2, components of hemidesmosomes that attach basal keratinocytes to the basement membrane zone. Antibody binding triggers subepidermal separation with tense, intact bullae and negative Nikolsky sign. Desmosomal targets define pemphigus vulgaris, which shows flaccid intraepidermal blisters with positive Nikolsky sign, the key discriminating feature.

Reference: Robbins and Cotran Pathologic Basis of Disease, 10th ed.

High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP

Written and medically reviewed by the StethoPrep medical team.