A 70-year-old man presents with tense blisters on an urticarial base on the trunk and flexures. Histopathology shows subepidermal blistering with eosinophilic infiltrate. Salt-split skin immunofluorescence shows IgG deposits on the roof (epidermal side) of the split. The target antigen is most likely:
- A BP180 (BPAG2/Type XVII collagen) NC16A domain ✓
- B Desmoglein-3 at the dermoepidermal junction
- C Laminin-332 (formerly laminin-5) on the floor side
- D Type VII collagen in the sub-lamina densa zone
Correct answer: A. BP180 (BPAG2/Type XVII collagen) NC16A domain
Explanation
Bullous pemphigoid targets BP180 (BPAG2/collagen XVII) and BP230. The NC16A domain of BP180 is the immunodominant epitope targeted by IgG and IgE autoantibodies. Salt-split skin technique splits through the lamina lucida: bullous pemphigoid antibodies bind to the roof (epidermal side) where BP180 is located. Laminin-332 antibodies (cicatricial pemphigoid) and type VII collagen antibodies (epidermolysis bullosa acquisita) deposit on the floor (dermal side) of the salt split. Desmoglein-3 is intraepidermal (pemphigus), not at the DEJ.
Reference: Neena Khanna Illustrated Synopsis of Dermatology & STD, 6th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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