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Pemphigus Vulgaris Diagnosis — MFDS Part 1 MCQ

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HardOral MedicinePemphigus Vulgaris DiagnosisMFDS Part 1

A 52-year-old woman has an 8-week history of painful oral erosions and transient flaccid blisters affecting the buccal mucosa and palate. The lesions heal without scarring, and gentle lateral pressure causes epithelial sloughing. Which investigation result would most reliably confirm the suspected diagnosis of pemphigus vulgaris?

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Correct answer: B — Perilesional mucosal direct immunofluorescence showing intercellular IgG around keratinocytes

Pemphigus vulgaris is most reliably confirmed by direct immunofluorescence of perilesional mucosa, showing intercellular IgG, often with C3, around keratinocytes in a net-like or “fishnet” pattern. The painful, fragile oral blisters, positive Nikolsky phenomenon and absence of scarring support an intraepithelial blistering disorder. Suprabasal acantholysis on routine histology is strongly supportive but is not as definitive as tissue immunofluorescence. Linear IgG and C3 along the basement membrane and circulating basement-membrane antibodies favour a pemphigoid disorder. Shaggy fibrinogen deposition at the basement membrane is associated with a lichenoid tissue reaction rather than pemphigus vulgaris.

Reference: van Beek N, et al. State-of-the-art diagnosis of autoimmune blistering diseases, diagnostic approach and direct immunofluorescence findings, 2024. https://pubmed.ncbi.nlm.nih.gov/37268547/