Mucous Membrane Pemphigoid
Mucous membrane pemphigoid (MMP) is the designation given to a heterogeneous group of rare chronic autoimmune disorders that tend to cause waxing and waning bullous lesions of the mucous membranes, often with subsequent scarring and morbidity.
(Synonyms of mucous membrane pemphigoid that are no longer used include cicatricial pemphigoid, ocular cicatricial pemphigoid, and benign mucous membrane pemphigoid.)
Oral MMP and ocular MMP are typical, but other mucosal sites and the skin (usually of the head and upper trunk) may be involved. The elderly are most often affected, women more than men.
Mucous membrane pemphigoid is characterized by subepithelial lesions caused by autoantibodies against molecules of epithelial basement membranes. The target molecules in MMP lie deep to 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. Anti-laminin-332 MMP is associated with an increased risk of internal cancer.
Treatment of mucous membrane pemphigoid is similar to that for bullous pemphigoid. Topical or intralesional corticosteroids and a combination of oral doxycycline 100 mg po bid and nicotinamide 500 mg po tid 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.