Mucous Membrane Pemphigoid

Mucous membrane pemphigoid is an uncommon, chronic blistering disorder affecting the mouth [186]. Other sites of involvement include the eyes, skin, and mucosa of the nasopharynx, anogenital region, oesophagus and larynx [32]. It has been defined as a group of putative autoimmune, chronic inflammatory, subepithelial blistering diseases predominantly affecting mucous membranes and characterised by linear deposition of IgG, IgA and C3 along the epithelial basement membrane [33]. It has also been called benign mucous membrane pemphigoid and cicatricial pemphigoid. However, it can be a severely disabling condition, and rarely causes scarring except in the eye and oesophagus/larynx, so these terms are not appropriate.

Mucous membrane pemphigoid is more common in women than men and most patients are in the 40-60-year age range. The mouth is often the first and only site of involvement. Oral lesions can be intact blisters that may contain clear or sero-sanguinous fluid, er-ythematous patches or superficial ulcers. Lesions are most common on the attached gingiva, usually buccal-ly and labially, and the palatal mucosa. Less frequent sites include the labial, lingual and buccal mucosae. Ocular lesions are characterised by conjunctival inflammation, ulceration and symblepharon due to fusion of the palpebral and bulbar conjunctivae. There may be severe scarring, entropion and blindness. Skin lesions are uncommon and usually involve the scalp and upper torso.

Microscopy shows subepithelial blister formation with clean separation of the full thickness of the epithelium from the underlying connective tissue (Fig. 3.3). There is usually a dense mixed inflammatory infiltration of the corium. Due to the strongly positive Nikolsky phenomenon seen in mucous membrane pemphigoid, it is very common to receive a biopsy specimen where most or all of the epithelium has been lost or completely separated from the connective tissue. The specimen then consists of non-specifical-ly inflamed connective tissue, which lacks the surface fibrinous slough that would be more typical of a nonspecific oral ulcer. This type of appearance, though not diagnostic, is highly suggestive of mucous membrane pemphigoid.

Direct immunofluorescence on peri-lesional mucosal biopsies shows continuous deposits of IgG, IgA or C3, either singly or in combination, along the basement membrane zone (BMZ) in about 80% of cases. When present, these deposits help to distinguish mucous membrane

Fig. 3.3. Mucous membrane pemphigoid showing clean subepi-thelial blistering

Fig. 3.4. Dermatitis herpetiformis showing polymorphonuclear leukocytes at the tips of the papillary corium pemphigoid from several other common oral muco-sal inflammatory disorders. For example, lichen planus does not have linear immunoglobulin deposits, but has linear and shaggy deposits of fibrin in the BMZ, and erythema multiforme has no linear BMZ deposits. However, these deposits do not distinguish mucous membrane pemphigoid from bullous pemphigoid, epidermolysis bullosa aquista or linear IgA bullous dermatosis. Such distinctions should be made on the basis of clinical findings.

Several possible target antigens have been identified in the sera of patients with mucous membrane pemphigoid. These include: bullous pemphigoid antigens 1 and 2; laminins 5 and 6; type VII collagen and 64 integrin subunit [32].

ing ulceration. In conventional gluten-sensitive enteropathy oral ulcers tend to be of the typical minor aphthous stomatitis type.

Microscopically, the lesions of dermatitis herpetiformis show polymorphonuclear leukocyte microabscesses in the tips of the papillary corium (Fig. 3.4). Initially, neutrophils predominate, but as the microabscesses enlarge eosinophils become more conspicuous. The mi-croabscesses eventually fuse to form visible blisters that frequently rupture leaving superficial ulcers. Direct immunofluorescence shows granular deposits of IgA in the BMZ of the dermal papillae, in both affected and adjacent normal mucosa.

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