Pemphigoid is a term used to refer to a group of cutaneous conditions that mainly manifest with blistering. Although similar in presentation to pemphigus, these blistering skin diseases occur without acantholysis, or the destruction of intercellular connections and the cohesion of adjacent keratinocytes of the skin. This condition tends to occur more frequently in women and in the elderly.
Diseases of this group are skin blistering or bullous diseases caused by the deposition of immune proteins called antibodies, or immunoglobulins, in the basement membrane of the epithelial layers. As such, they can be classified according to what immunoglobulin is involved. Pemphigoid gestationis (PG), bullous pemphigoid (BP), and mucous membrane or cicatricial pemphigoid (MMP/CP) all involve immunoglobulin G (IgG). Another classification called immunoglobulin A (IgA) pemphigoid involves IgA.
As the name implies, PG, or herpes gestationis, is associated with pregnancy, usually appearing in the second or third trimester or immediately after delivery. MMP/CP and BP generally affect people of ages 60 years and above. While MMP/CP does not involve the skin, BP rarely affects the mouth.
In BP, skin involvement includes the inner surfaces of the thighs, flexor aspects of the forearms, groin, armpits, and lower legs, and may be associated with hive-like lesions and extreme itchiness or pruritus. Some people with this condition may have oral blisters, which appear after the skin blisters. The lesions are tense blisters, or bullae, filled with a clear fluid and found on normal or reddish skin. These blisters generally have an average diameter of 0.8 inch (2 cm), but may reach 1.6 to 3.1 inches (4 to 8 cm) at times.
The BP blisters reach only the subepidermis and not the dermis, thus they are neither prone to rupture nor scarring. Nevertheless, rupture of the bullae leads to ulceration. This makes the skin prone to secondary bacterial infection that could reach the dermis, leading to scarring.
Pemphigoid is often a diagnosis of exclusion, given after inflammatory and infectious causes of acute or chronic blistering have been ruled out. Diagnosis involves the proper examination of the skin lesions, a skin biopsy, and an immunohistological method called direct immunofluorescence. Upon microscopic examination of the biopsied skin, pemphigoid would show a vacuolated basal cell layer extending only subepidermally, without acantholysis. On direct immunofluorescence of the biopsy sample, desmoglein antibodies would test positive. An enzyme-linked immunosorbent assay (ELISA) test has been developed for detecting desmoglein antibodies present in the blood.
Treatment of this chronic blistering disease involves the administration of topical or oral corticosteroids to reduce the production of antibodies. Examples include prednisolone and prednisone. Other treatment options include dapsone, erythromycin, cyclosporine, cyclophosphamide, azathioprine, and mycophenolate mofetil.