Vesiculobullous Lesions of Oral Mucosa
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Direct answer
Split level is everything in oral vesiculobullous disease: pemphigus vulgaris splits intraepithelially just above the basal layer through autoantibody-driven acantholysis (IgG against desmoglein 3, later desmoglein 1), leaving rounded dissociated Tzanck cells and fragile flaccid blisters that shear into painful irregular erosions, with a positive Nikolsky sign; mucous membrane pemphigoid splits beneath the whole epithelium (IgG/C3 against the basement membrane zone, classically BP180), producing tense subepithelial blisters, desquamative gingivitis and scarring of conjunctiva and other mucosae; bullous pemphigoid is its elderly, skin-dominant, non-scarring cousin; and erythema multiforme (with its severe Stevens-Johnson spectrum) delivers target lesions after HSV or drug triggers without autoantibody. Because intact oral bullae rarely survive mastication, the clinician usually meets erosions only — so diagnosis rests on biopsy of perilesional tissue for H and E plus a second biopsy for direct immunofluorescence, whose patterns (fishnet intercellular IgG, linear basement-membrane IgG/C3, shaggy fibrin) are among the most reliably examined facts in NEET-MDS oral pathology.
What you must remember
- Pemphigus vulgaris: IgG against desmoglein 3 (mucosal-dominant) with desmoglein 1 added when skin involved; suprabasal split with intact basal row ("row of tombstones"); acantholytic Tzanck cells; oral lesions precede skin disease in over half of patients, flaccid bullae rupture to leave broad erosions; positive Nikolsky; untreated historically fatal, now controlled with systemic corticosteroids and rituximab.
- Mucous membrane pemphigoid (cicatricial pemphigoid): subepithelial split, linear IgG and/or C3 at the basement membrane; desquamative gingivitis plus symblepharon and scarring of eyes, nose, oesophagus; predominantly older women; dapsone and steroids; rituximab for refractory ocular disease.
- Bullous pemphigoid: elderly, tense cutaneous bullae, antibodies to BP180 (type XVII collagen) and BP230; oral involvement mild or absent; excellent prognosis compared with pemphigus.
- Linear IgA disease: "string of pearls" bullae in children and adults, linear IgA on DIF; vancomycin among the implicated drugs.
- Erythema multiforme / Stevens-Johnson / TEN: target lesions, self-limited HSV- or drug-triggered episodes (sulphonamides, anticonvulsants, NSAIDs), apoptotic keratinocytes, DIF negative or non-specific; treatment is trigger elimination and supportive care.
- Nikolsky sign: sliding tangential pressure shears epithelium in pemphigus (sometimes pemphigoid, toxic epidermal necrolysis); Asboe-Hansen sign is blister extension under direct pressure.
- Hereditary epidermolysis bullosa: junctional (laminin-332, collagen XVII defects) and dystrophic (COL7A1) forms blistering from birth — the genetic end of the subepithelial split spectrum.
- Dermatitis herpetiformis: granular IgA at dermal papillae, intensely pruritic elbows-and-knees papulovesicles, gluten-sensitive enteropathy association — a favourite cross-connection to coeliac disease.
Reading the biopsy in three steps
A 38-year-old woman has six weeks of painful, ragged oral erosions involving palate, buccal mucosa and gingiva, plus a few flaccid trunk bullae. Step one: histology from the edge of a fresh erosion shows an intraepithelial cleft just above the basal layer — basal cells still attached to the lamina propria like a row of tombstones — with large rounded acantholytic Tzanck cells floating in the cleft. This is suprabasal acantholysis, and the shortlist collapses to pemphigus vulgaris. Step two: direct immunofluorescence of perilesional mucosa shows intercellular IgG and C3 throughout the epithelium — the fishnet pattern — and ELISA desmoglein 3 titres track disease activity. Step three: stage the patient — screen skin and other mucosae, initiate systemic therapy (high-potency steroids with a steroid-sparing agent; rituximab is standard for moderate-severe disease), and arrange dental care. Contrast a 62-year-old with tense gingival sloughing and symblepharon showing a subepithelial split with linear C3-IgG at the basement membrane — pemphigoid — whose management pivots to ophthalmology because scarring, not the mouth, threatens sight.
Where students slip
The commonest error is diagnosing from blister appearance — intact oral bullae are rare, and flaccid-versus-tense is a skin sign, so the oral examiner wants split level plus immunofluorescence. Second, Tzanck smear findings are misattributed: the acantholytic Tzanck cell of pemphigus is a single rounded epithelial cell, whereas multinucleated giant cells belong to herpesviruses — a deliberate confusion in image-based questions. Third, therapy is mixed up (rituximab has strong evidence in pemphigus; dapsone in pemphigoid) and desmoglein numbers swapped (3 is mucosal, 1 is superficial skin). Finally, erythema multiforme is filed as autoimmune; it is an immune-mediated reaction pattern with negative DIF, and its HSV association explains the recurrent autumn-winter form.
Frequently asked questions
What is the level of split in pemphigus vulgaris versus pemphigoid?
Pemphigus vulgaris splits intraepithelially, just above the basal layer (suprabasal acantholysis), while mucous membrane pemphigoid splits beneath the entire epithelium at the basement membrane zone.
Which antibodies define pemphigus vulgaris?
IgG autoantibodies against desmoglein 3 in mucosal disease, with anti-desmoglein 1 appearing when skin is involved; DIF shows intercellular fishnet IgG/C3 staining.
What is the Nikolsky sign?
Sliding tangential pressure on clinically normal skin or mucosa causes epithelial shearing — characteristic of pemphigus vulgaris and also seen in toxic epidermal necrolysis.
Which vesiculobullous disease causes ocular scarring?
Mucous membrane (cicatricial) pemphigoid, through linear basement-membrane-zone antibodies producing subepithelial blistering and symblepheron formation.
How does erythema multiforme differ immunopathologically from pemphigus?
It is an immune-mediated reaction to HSV or drugs with target lesions, apoptotic keratinocytes and negative direct immunofluorescence — no autoantibody-mediated split.