A 45-year-old woman presents with tense bullae predominantly on the inner thighs, flexures, and abdomen. The Nikolsky sign is negative. DIF of perilesional skin shows linear IgG and C3 at the BMZ. ELISA is positive for anti-BP180 NC16A domain antibodies. Which autoantigen is targeted in the transmembrane collagenous domain responsible for triggering the complement pathway?

• A BP230 (BPAG1)
• B BP180 NC16A extracellular domain (BPAG2) ✓
• C Desmoglein-3
• D Laminin-332 (epiligrin)

Explanation

Bullous pemphigoid (BP) is caused by IgG autoantibodies primarily against the NC16A domain of BP180 (type XVII collagen/BPAG2), a transmembrane collagen in the lamina lucida. This domain is the major immunodominant region targeted in BP. Complement activation via C3 deposition leads to mast cell degranulation and neutrophil/eosinophil recruitment causing subepidermal blister formation. BP230 (BPAG1) is an intracellular plakin; anti-BP230 antibodies also occur but NC16A antibodies correlate best with disease activity. Laminin-332 targeting causes MMP with high malignancy risk.

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.