Bullous pemphigoid is a rare skin condition that causes large, fluid-filled blisters on areas of skin that often flex — such as the lower abdomen, upper thighs or armpits.
Bullous pemphigoid is most common in people older than age 60 and can occur when your immune system attacks a thin layer of tissue below your outer layer of skin (just under the epidermis). The cause for this abnormal immune response is unknown.
What causes bullous pemphigoid?
Though what causes bullous pemphigoid isn’t really known, a form of this condition (drug-induced pemphigoid) may be triggered by drugs such as some antibiotics. Ultraviolet light therapy, sometimes used to treat other skin conditions, and radiation therapy used to treat cancer, may also trigger an outbreak. The blisters occur because of a malfunction in the immune system. Your body's immune system normally produces antibodies to fight infectious microbes. Patients with bullous pemphigoid develop antibodies by mistake to their own skin. Specifically the antibodies recognize the basement membrane, a thin layer of fibers which anchor the outer layer of skin (epidermis) to the next layer of skin (dermis). These antibodies interrupt the connections which leads to blisters.
Symptoms of bullous pemphigoid
The primary symptom of bullous pemphigoid is the appearance of large blisters that don't easily rupture when touched. The fluid inside the blisters is usually clear but may contain some blood. The skin around the blisters may appear normal or red.
These blisters often appear on the lower abdomen, groin, upper thighs and arms. Blisters may also be located along creases or folds in the skin, such as the skin on the inner side of a joint. The affected areas of skin can be very itchy.
You might also develop blisters or sores in your mouth. Rarely, the mucous membranes of the eyes can be involved, creating redness, soreness and discomfort. Some subset of patients with pemphigoid do not develop blisters.
Diagnosing bullous pemphigoid
We perform the following tests in order to properly diagnose you with bullous pemphigoid:
Skin biopsy. This will show the presence of a blister under the epidermis as well as inflammatory cells in the dermis.
Direct immunofluorescence. This is done to shows an immune-mediated disease process. Autoantibody immunoglobulin G (IgG) is deposited in a line along the dermoepidermal junction.
Indirect immunofluorescence. This is a blood test to reveals the presence of circulating IgG autoantibodies that target the skin basement membrane and type VII collagen.
Treatment may require corticosteroids, such as prednisone, and other drugs that suppress the immune system. Many patients can be managed with topical therapies. Bullous pemphigoid can be life-threatening, especially for those who are already in poor health, so please make an appointment at the Dermatological Center for Skin Health if you suspect an outbreak. Some patients are able to eventually use only topical therapies to control their disease.