Bullae are elevated, fluid-filled blisters ≥ 10 mm in diameter.
(Synonyms of mucous membrane pemphigoid that are no longer used include cicatricial pemphigoid, ocular cicatricial pemphigoid, and benign mucous membrane pemphigoid.)
Oral mucous membrane pemphigoid and ocular mucous membrane pemphigoid are typical, but other mucosal sites and the skin (usually of the head and upper trunk) may be involved. Older people are most often affected, women more than men.
Mucous membrane pemphigoid (MMP) is characterized by subepithelial lesions caused by autoantibodies against molecules of epithelial basement membranes. The target molecules lie deeper than those of bullous pemphigoid. Several autoantibodies have been identified, including those against BPAG2, laminin-332, and type VII collagen. Antibodies to beta-4 integrin have been identified in generalized MMP and ocular MMP, and antibodies to alpha-6 integrin have been identified in oral MMP.
Prevalent mucosal involvement and scarring lesions help distinguish MMP from bullous pemphigoid. Diagnosis of mucous membrane pemphigoid is supported by lesion biopsy and direct immunofluorescence. Linear basement membrane deposits may include IgG, IgA, and C3. Serum autoantibodies tend to be absent or at low titre.
Mucous membrane pemphigoid progresses slowly, rarely remits spontaneously, and often responds incompletely to treatment. Depending on the site affected, serious sequelae may include ocular damage and blindness, airway erosions and destruction, and strictures of the esophagus or anogenital regions. Patients with anti-laminin-332 MMP have an increased risk of internal cancer; if this form is suspected (eg, by immunofluorescence results), patients should be screened for cancers common to their age and sex.
Treatment of mucous membrane pemphigoid is similar to that for bullous pemphigoid. Topical or intralesional corticosteroids and a combination of oral doxycycline 100 mg orally twice a day and nicotinamide 500 mg orally 3 times a day may be useful for milder cases.
Severe disease may require systemic immunosuppression with dapsone or prednisone or sometimes high-dose prednisone with immunosuppressants (eg, azathioprine, mycophenolate, cyclophosphamide, rituximab) and IV immune globulin.