Which type of biopsy is indicated for mucous membrane pemphigoid?

Correct answer: B. Incisional (perilesional) biopsy

• A. Brush biopsy collects surface cells only and cannot demonstrate the level of the split or the immunofluorescence pattern.
• B. Correct. An INCISIONAL biopsy taken from PERILESIONAL tissue — intact epithelium immediately adjacent to the lesion — is required, with one specimen in formalin for H&E and a second in Michel's medium for DIRECT IMMUNOFLUORESCENCE, which shows a linear band of IgG and C3 at the basement membrane zone.
• C. Excisional biopsy is for small, discrete lesions that can be removed entirely; it is not appropriate for a diffuse desquamative process.
• D. Culture and sensitivity applies to infection, which this is not.

Note: Do NOT biopsy the ulcer bed itself — the epithelium there has already been lost and the specimen will be non-diagnostic.