Two white lesions and a brown one

Correct answer: B. White sponge nevus

• A. Reticular lichen planus produces fine lacy Wickham striae rather than a thick folded plaque, and it appears in adulthood without a family history.
• B. Correct. White sponge nevus is an autosomal dominant condition caused by mutations in keratin 4 or 13. It produces a thick, spongy, folded, symmetrical white lesion, most obviously on the buccal mucosa but also on the floor of the mouth, and it may involve nasal, oesophageal and anogenital mucosa. It appears in childhood, is asymptomatic and needs no treatment. The family history is the strongest clue.
• C. Pseudomembranous candidiasis wipes off to leave an erythematous base, which this does not.
• D. Carcinoma of the floor of the mouth would be an indurated ulcer or a firm irregular mass in an older patient with tobacco and alcohol exposure. It would not be diffuse, spongy, symmetrical or lifelong.

Correct answer: C. Leukoedema

• A. Nicotinic stomatitis affects the hard palate, producing a grey-white surface studded with red inflamed salivary duct openings.
• B. Lichen planus shows lacy striae and often erosive areas, and it does not disappear when the tissue is stretched.
• C. Correct. Leukoedema is a normal variation, especially common in individuals with darker pigmentation. It is bilateral, diffuse, greyish-white and filmy, and the diagnostic manoeuvre is stretching the cheek, which makes it disappear and reappear on release. It is caused by intracellular oedema of the spinous layer and requires no treatment.
• D. Leukoplakia is a persistent white plaque that does not fade on stretching and is a diagnosis of exclusion carrying malignant potential.

Correct answer: A. Oral submucous fibrosis

• A. Correct. Areca nut, the active component of betel quid, causes progressive submucosal fibrosis. Collagen accumulates and the mucosa becomes pale, marbled and stiff, with palpable fibrous bands and progressive trismus. Betel staining accompanies it. It carries a substantial risk of malignant transformation and needs long-term surveillance.
• B. Lichen planus produces striae and erosions and does not cause dense fibrosis with trismus.
• C. Erythroplakia is a velvety red patch with high dysplasia risk. It could arise on this background, but the fibrosis and trismus described define submucous fibrosis.
• D. An amalgam tattoo is a solitary blue-grey macule next to a restored tooth, not diffuse staining with fibrosis and restricted opening.

Correct answer: D. A choristoma

• A. Hyperplasia is an increase in cell number in response to a stimulus, in the correct location.
• B. A teratoma contains tissue from more than one germ layer and is a true neoplasm.
• C. A hamartoma is disorganised overgrowth of tissue that is native to the site, for example a haemangioma or an odontoma.
• D. Correct. A choristoma is histologically normal tissue in a site where it does not belong. The oral examples are the osseous and cartilaginous choristomas of the tongue and Fordyce granules, which are sebaceous glands in the buccal mucosa where no skin exists.

Correct answer: C. Pyogenic granuloma

• A. A peripheral ossifying fibroma is firmer, paler, and shows radiopaque foci within it on radiographs.
• B. A peripheral giant cell granuloma is usually more blue-purple, arises only on gingiva or alveolar ridge, and may cause superficial cupping resorption of underlying bone.
• C. Correct. Pyogenic granuloma is a reactive proliferation of granulation tissue driven by local irritation such as calculus or a restoration margin. It is soft, red to purple, pedunculated, grows quickly and bleeds with minimal provocation. Pregnancy raises the incidence but is not required for the diagnosis. Treatment is excision with removal of the local irritant.
• D. Carcinoma in a 28-year-old with this presentation would be very unusual; it presents as an indurated non-healing ulcer rather than a soft bleeding pedunculated mass.

Correct answer: D. Nicotinic stomatitis

• A. A lipoma presents as a soft, yellowish, sometimes fluctuant submucosal mass and is a legitimate consideration.
• B. A traumatic fibroma is the single most common submucosal nodule of the buccal mucosa, arising along the occlusal line from cheek biting.
• C. A schwannoma is a benign nerve sheath tumour that presents as a slow-growing, painless, firm submucosal nodule and belongs in the differential.
• D. Correct, and this is the exception. Nicotinic stomatitis is a diffuse surface change of the hard palate, a grey-white keratosis with red punctate duct openings. It is neither a nodule nor a buccal mucosa lesion, so it does not belong in this differential.

Correct answer: B. Topical clobetasol

• A. Acyclovir treats herpesvirus infection, which produces vesicles and ulcers without striae or Civatte bodies.
• B. Correct. Civatte bodies are apoptotic basal keratinocytes, the histological signature of lichen planus alongside a band-like lymphocytic infiltrate and basal cell degeneration. Symptomatic erosive disease is treated with a potent topical corticosteroid, and clobetasol propionate is the standard choice, with antifungal cover if candidiasis supervenes.
• C. Antibiotics have no role; lichen planus is immune-mediated, not bacterial.
• D. Clotrimazole treats candidiasis, which frequently overlies lichen planus but is not the primary disease being treated here.

Correct answer: C. Ophthalmologist

• A. Renal involvement does not feature in mucous membrane pemphigoid.
• B. There is no endocrine association with pemphigoid.
• C. Correct. Subepithelial separation at the basement membrane zone indicates mucous membrane pemphigoid. Its most serious complication is ocular involvement: conjunctival scarring, symblepharon and, if unrecognised, blindness. Ophthalmological referral is urgent even when the eyes appear normal, because early disease is easily missed.
• D. Haematological referral would be relevant to a bleeding or marrow disorder, not to a subepithelial blistering disease.

Note: Contrast this with pemphigus vulgaris, in which the split is intraepithelial from acantholysis, direct immunofluorescence shows a fishnet pattern, and the Tzanck test shows acantholytic cells.

Correct answer: C. Systemic lupus erythematosus

• A. Rosacea produces central facial erythema with telangiectasia and papulopustules, and it does not spare the nasolabial folds in the characteristic butterfly pattern.
• B. Contact dermatitis follows the pattern of exposure to an allergen and would not respect this symmetrical malar distribution.
• C. Correct. The malar or butterfly rash spans both cheeks and the nasal bridge while sparing the nasolabial folds, and is one of the classification criteria for SLE. Oral findings include palatal ulceration and lichenoid lesions, and patients may carry secondary Sjogren, antiphospholipid antibodies or be taking immunosuppressants that affect dental care.
• D. Seborrhoeic dermatitis gives greasy scaling in the nasolabial folds, eyebrows and scalp, which is close to the opposite distribution.