Recent advances in molecular pathology have lead to the discovery of various target antigens that are responsible for various blistering diseases, some of which affect the oral mucous membranes. In an attempt to clarification and combining the molecular aspects with the clinical presentation of those diseases some authors have proposed the general term of "Immune mediated subepithelial blistering diseases of mucous membranes". This term is an umbrella under which the following diseases can be grouped: mucous membrane pemphigoid (MMP), bullous pemphigoid (BP), cicatricial pemphigoid (CP), ocular cicatricial pemphigoid (OCP), herpes gestationis, linear IgA disease and some variants of epidermolysis bullosa among others. The dermatologists generally use the term CP to refer to MMP. Mucous membrane pemphigoid (MMP) is an autoimmune disorder almost exclusively affecting the oral mucosas which occasionally may present ocular manifestations in which case it might represent a combination with ocular cicatricial pemphigoid (CP). Bullous pemphigoid (BP) is an autoimmune disorder almost exclusively affecting the skin with occasional intraoral manifestations.
MMP, CP and BP are similar in that autoantibodies are directed to proteins that form part of the adhesion mechanism of the mucosal epithelium to the basal membrane. These proteins are treated as antigen by IgG antibodies with consequent separation of the epithelium from the subjacent connective tissue and formation of infraepithelial vesicles. Several antigenic proteins have been identified for each one of the diseases in this group and some times in combination, the one affected in MMP is known as BP-1 antigen which is a 230-kDa protein found in the hemidesmosomes of the epithelial basal cell layer. Recently another protein known as BP-2 antigen (a 180-kDa protein) also has been identified in patients with MMP. A couple of rare diseases also affecting the oral mucosas with infraepithelial blister formation have been described. The target antigens in these diseases are other adhesive proteins found in the epithelium basal membrane complex interaction. The clinical oral manifestations of any of these disorders are essentially similar and their proper typing is only achieved by complex laboratory testing which include immunofluorescence as the basic procedure. This drawing schematically demonstrates the separation of the keratinocytes from the basal membrane with eventual formation of a subepitelial blister.