Mucous membrane pemphigoid (MMP) is the clinical phenotype of a group of autoimmune blistering diseases characterized by autoantibodies directed against different structural proteins in epidermal basement membranes. The clinical course and prognosis of MMP are affected by the specific autoantigen targeted, the titer and bioactivity profile of corresponding autoantibodies, and the specific mucosal sites of disease activity. Irreversible scarring and loss of function must be prevented by early diagnosis and appropriate interventions.