A patient has buccal mucosa that peels with slight manipulation, burning after spicy food, and generalised desquamative gingivitis with erythematous swollen gingiva (positive Nikolsky sign). Which of the following can NOT be part of the differential diagnosis?

Correct answer: A. Recurrent aphthous ulceration

• A. Correct. Aphthous ulcers are discrete, punched-out, non-desquamating ulcers on NON-keratinised mucosa. They do not produce a positive Nikolsky sign or generalised desquamative gingivitis.
• B. Incorrect. Pemphigus vulgaris is a classic cause of desquamative gingivitis with a positive Nikolsky sign.
• C. Incorrect. Erosive lichen planus completes the classic triad presenting as desquamative gingivitis.
• D. Incorrect. Mucous membrane pemphigoid is one of the three principal causes of desquamative gingivitis.