Oral Mucosal Diseases and Mucocutaneous Disorders
Domain 3 tests pattern recognition and the biopsy pathway for white, red, ulcerative, and vesiculobullous mucosal disease. The exam rewards a precise description of distribution and morphology, because that description determines whether you biopsy, test with DIF, or treat empirically.
White and red lesions
- Leukoplakia is a white patch that cannot be classified as another disease; persistent lesions require biopsy, especially nonhomogeneous lesions.
- Erythroplakia is a red velvety patch with high malignant potential and mandates biopsy.
- Oral lichen planus is usually bilateral with reticular striae on buccal mucosa and gingiva; erosive disease is symptomatic. Biopsy with DIF helps exclude lichenoid lesions; malignant transformation is about 1%.
- Oral lichenoid lesions are often unilateral and temporally related to a drug or amalgam; they may resolve after removal of the trigger.
- Candidiasis presents as pseudomembranous, erythematous, or hyperplastic disease; risk factors include antibiotics, steroids, xerostomia, diabetes, and HIV.
Vesiculobullous disease
- Pemphigus vulgaris causes flaccid bullae, oral lesions often precede skin disease, Nikolsky sign is positive, and DIF shows intercellular IgG; anti-desmoglein 3 is typical.
- Mucous membrane pemphigoid causes tense bullae, gingival desquamation, and ocular involvement; DIF shows linear IgG and C3 at the basement membrane.
- Erythema multiforme causes target lesions and is often triggered by HSV.
- Angina bullosa haemorrhagica produces blood blisters that resolve spontaneously.
Ulcers
- Recurrent aphthous stomatitis includes minor, major, and herpetiform types.
- Herpes simplex causes clustered vesicles and gingivostomatitis; recurrent herpes labialis is common.
- Squamous cell carcinoma presents as a persistent, indurated ulcer with fixity or lymphadenopathy.
Worked example
A 45-year-old woman has desquamative gingivitis. The differential includes oral lichen planus, mucous membrane pemphigoid, pemphigus vulgaris, plasma cell gingivitis, and a lichenoid drug reaction. Biopsy with DIF is required. If MMP is suspected, refer for ophthalmologic assessment because conjunctival scarring can cause blindness.
Traps that cost marks
- Treating erosive lichen planus with surgical excision.
- Missing ocular symptoms in mucous membrane pemphigoid.
- Calling every ulcer aphthous and missing malignancy.
- Omitting DIF when autoimmune blistering is possible.
- Using topical steroids before biopsy without considering the effect on histology.