Skin biopsy from a patient with chronic prurigo-like lesions shows subepidermal blister with an infiltrate predominantly of eosinophils. DIF of perilesional skin shows linear IgG and C3 at the basement membrane zone (BMZ). Salt-split skin DIF localises the IgG to the epidermal side of the split. What is the diagnosis?

• A Epidermolysis bullosa acquisita (EBA)
• B Bullous pemphigoid ✓
• C Linear IgA disease
• D Mucous membrane pemphigoid

Explanation

In bullous pemphigoid (BP), DIF shows linear IgG and C3 at the BMZ. On salt-split skin (using 1 mol/L NaCl which splits through the lamina lucida), BP antibodies bind to the epidermal side because BP180 and BP230 are localized there. In EBA and mucous membrane pemphigoid targeting type VII collagen (lamina densa/sub-lamina densa), antibodies bind to the dermal side of the split. Linear IgA disease shows linear IgA on DIF. This epidermal-side localisation on salt-split confirms BP.

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.