Mucous Membrane Pemphigoid
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Direct answer
Mucous membrane pemphigoid, also called cicatricial pemphigoid, is a chronic subepidermal autoimmune blistering disease that mainly affects the mouth, eyes, nose, pharynx and genitals. Its defining feature is scarring, which can lead to blindness through symblepharon and corneal damage, and antibodies to BP180 and laminin 332 drive it. Direct immunofluorescence shows linear IgG or C3 at the basement membrane zone, and treatment usually needs systemic immunosuppression with close ophthalmic follow-up.
What you must remember
- Antigens: BP180 (type XVII collagen), laminin 332 and integrin beta-4 are the principal targets, with anti-laminin 332 antibodies linked to an increased risk of underlying solid malignancy.
- Sites: the oral mucosa is the commonest site, followed by the conjunctiva, nose, pharynx, larynx, oesophagus and genitalia.
- Ocular disease: conjunctivitis progresses to symblepharon, trichiasis, entropion and corneal damage, which can cause blindness.
- Skin: tense bullae and erosions on the head, neck and upper trunk, usually less prominent than the mucosal disease.
- Histology: a subepidermal blister with a mixed infiltrate, often with eosinophils, similar to bullous pemphigoid.
- Immunofluorescence: linear IgG, IgA or C3 along the basement membrane zone, with salt-split skin used to localise the binding site.
- Treatment: topical steroids for mild disease, with dapsone for mild-to-moderate disease, and systemic steroids with cyclophosphamide or rituximab for severe or ocular disease.
A stepwise plan from mapping to surveillance
A patient with scarring conjunctivitis and gingival erosions shows why this disease is managed by a team rather than by the dermatologist alone. The steps below run from site mapping to long-term surveillance.
- Map the mucosal sites. Document oral, ocular, nasal, pharyngeal, laryngeal and genital involvement, since each site carries a different risk.
- Examine the eyes early. Slit-lamp review looks for conjunctival scarring, symblepharon and trichiasis, because damage can progress quietly.
- Biopsy for histology and direct IF. A biopsy from an active margin shows a subepidermal split, and linear basement membrane deposition confirms the diagnosis.
- Test circulating antibodies. Assays for BP180 or laminin 332 help characterise the disease, but a negative result does not exclude it.
- Stage the treatment. Use topical steroids for localised oral disease, and use dapsone for mild-to-moderate disease, and move to systemic steroids with cyclophosphamide or rituximab when eye or extensive disease is present.
- Follow up for scarring. Review eyes, airway, swallowing and genital function regularly, since treatment often slows rather than reverses scarring.
Where candidates lose marks
Distinguishing this disease from pemphigus and bullous pemphigoid depends on scarring, site and immunofluorescence.
- Trap: labelling an oral, scarring blister as pemphigus vulgaris Correct: the split is subepidermal without acantholysis, and direct IF shows linear basement membrane deposits rather than intercellular ones.
- Trap: believing topical steroids alone protect the eyes Correct: ocular disease needs systemic therapy and specialist review, since the cornea can be damaged despite topical measures.
- Trap: treating a negative circulating antibody test as proof of absence Correct: the diagnosis rests on histology and direct IF, and antibody assays are supportive only.
Frequently asked questions
Which antigens are targeted in mucous membrane pemphigoid?
BP180, also known as type XVII collagen, laminin 332 and integrin beta-4 are the main antigens in mucous membrane pemphigoid. Antibodies against laminin 332 have been linked to an increased risk of underlying solid malignancy.
Why is ocular involvement important in mucous membrane pemphigoid?
Ocular involvement can cause conjunctival scarring, symblepharon, trichiasis and corneal damage that may progress to blindness. Early ophthalmic review and specialist treatment are essential, even when the skin disease seems mild.
How does direct immunofluorescence help in mucous membrane pemphigoid?
Direct immunofluorescence shows linear deposits of IgG, IgA or C3 along the basement membrane zone, confirming a subepidermal blistering disease. This pattern separates it from pemphigus, where the deposits are intercellular.
Which drugs are used in mucous membrane pemphigoid apart from corticosteroids?
Dapsone is used in mucous membrane pemphigoid, particularly for milder disease, and steroid-sparing agents such as azathioprine, mycophenolate or cyclophosphamide are added in severe cases. The choice depends on the sites involved and the response.