A case of general erythematous gingivitis with focal ulceration, also affecting the eye. The most likely diagnosis is:

Correct answer: D. Mucous membrane pemphigoid (MMP)

• A. Pemphigus vulgaris can affect the oral mucosa but less commonly involves the eyes as a primary site.
• B. Oral lichen planus rarely causes significant ocular involvement.
• C. Stevens-Johnson syndrome is a severe drug reaction causing widespread mucocutaneous involvement including eyes; however, MMP is more chronic and the pattern of desquamative gingivitis with eye involvement is classic for MMP.
• D. Correct. MMP (cicatricial pemphigoid) is an autoimmune subepithelial blistering disease that frequently affects the oral mucosa (desquamative gingivitis pattern) and eyes (conjunctival scarring/symblepharon). Ocular involvement is a hallmark that distinguishes MMP from other bullous diseases.