Oral Manifestations of Autoimmune Blistering Diseases

[drmithila]

Causes
Autoimmune blistering diseases generally are caused by autoantibodies targeting the skin components of the epithelial cell surfaces or basement membrane zone. Certain human leukocyte antigen (HLA) alleles have been reported to be associated with autoimmune blistering diseases. For example, HLA-DQB1*0301 is associated strongly with bullous pemphigoid and mucous membrane pemphigoid.

Pemphigus group
Desmoglein-3 is the primary target antigen in pemphigus vulgaris, and desmoglein-1 is the exclusive target antigen in pemphigus foliaceus. In passive transfer experiments, these autoantibodies apparently induced (in newborn mice) blisters that have similar histology as the human diseases. These autoantibodies apparently are capable of inducing the blisters without the help of complement components; however, autoantibodies against desmoglein-1 are present in patients with pemphigus vulgaris and are capable of inducing blisters in newborn mice.

Paraneoplastic pemphigus
No true cause has been firmly established. Some patients have autoantibodies against desmoglein-3, and these autoantibodies can induce blisters in newborn mice. The possible link between the underlying neoplasm and autoimmunity may be due to an immune dysregulation secondary to the presence of neoplasm. In addition to autoantibodies to desmoglein-3, most patients develop autoantibodies to many intracellular epithelial components, desmoplakins I and II, periplakin, envoplakin, BP230 (BPAg1), and a 170-kd membrane protein. Several other smaller proteins are involved.

Autoantibodies to these intracellular components probably develop as a secondary autoimmune response rather than a primary cause. Neoplasms are clearly associated with paraneoplastic pemphigus. The most common associated benign tumor is thymoma, followed by Castleman tumor, a rare and complex lymphoproliferative disease. The most common associated malignant tumor is non-Hodgkin lymphoma, followed by chronic lymphocytic leukemia.

Pemphigoid group
Autoantibodies to BP180 are the likely inducing autoantigen. Passive transfer experiments using rabbit antimouse BP180 antibodies induce blisters in newborn mice, and the blister induction apparently is complement dependent. The target antigen for linear IgA bullous dermatosis (childhood and adult) is a truncated BP180 protein. The target antigen for epidermolysis bullosa acquisita is type VII collagen, particularly the noncollagenous (NC1) domain.

Mucous membrane pemphigoid
Multiple target antigens have been identified, including BP180, laminin-5, laminin-6, type VII collagen, and beta-4 integrin, but no clinical hallmark distinguishes subsets of patients with regard to the target antigen. Rabbit antibodies generated against laminin-5 can induce blisters in newborn mice. Presently, the link between the autoantibodies and the scarring process that characterizes this group of diseases is missing.