Pemphigus involves blistering of the outer (epidermal) layer of the skin and mucous membranes. It is an autoimmune disorder in which the immune system produces antibodies against specific proteins in the skin and mucous membrane. These antibodies produce a reaction that leads to a separation of epidermal cells (acantholysis). The exact cause of the development of antibodies against the body's own tissues (autoantibodies) is unknown.

Sometimes pemphigus appears due to reactions to medications, although this is rare. Pemphigus may be a side effect of ACE inhibitors (such as Elanapril) or chelating agents (such as penicillamine).

Pemphigus is uncommon. It occurs almost exclusively in middle-aged or older people, of all races and ethnic groups. About one-half of the cases of pemphigus vulgaris begin with blisters in the mouth, followed by skin blisters. The blisters (bullae) are relatively asymptomatic, but the lesions become widespread and complications develop rapidly and may be debilitating or fatal.