What is pemphigoid gestationis?
Pemphigoid gestationis is a rare pregnancy-associated autoimmune skin disease that is characterised by an itchy rash that develops into blisters. It is most common during the second and third trimesters of pregnancy. It was previously known as herpes gestationis although it has no association with the herpes virus whatsoever.
What causes pemphigoid gestationis?
Pemphigoid gestationis is an autoimmune blistering disease, which basically means that an individual's immune system starts reacting against his or her own tissue. Immunoglobulin type G (IgG) autoantibodies (known as the PG factor) cause the damage.
In pemphigoid gestationis the target is a protein known as BPAG2 (also called BP180), found within the basement membrane, which is the zone between the epidermis and the dermis (the top and middle layers of skin). BPAG2 is within the hemidesmosome, the cell component that sticks the epidermal keratinocyte cells to the dermis.
The antibody attack results in inflammation and separation of the epidermis from the dermis allowing fluid to build up and create a blister.
What are the signs and symptoms of pemphigoid gestationis?
Most patients present with an intensely itchy hive-like rash during mid to late pregnancy (13 to 40 weeks gestation).
- Initially there are itchy red bumps around the belly button
- Within days to weeks, the rash spreads to other parts of the body including the trunk, back, buttock, and arms. The face, scalp, palms, soles and mucous membranes are usually not affected.
- After 2-4 weeks, large, tense fluid-filled blisters form
- Some patients may have no blisters but instead have plaques (large raised patches)
In some cases, pemphigoid gestationis occurs throughout pregnancy. Symptoms may lessen or spontaneously resolve towards the end of the pregnancy but this is short-lived, as 75-80% of women will experience a flare-up around delivery. In most cases, symptoms resolve days later after giving birth, however in some, the disease remains active for months or years. Commencement of menstrual periods, use of oral contraceptives or further pregnancies may cause flare-ups.
Tests for pemphigoid gestationis
Diagnosis generally requires a skin biopsy, which shows typical features of subepidermal blistering, similar in microscopic appearance to bullous pemphigoid (BP) or epidermolysis bullosa acquisita (EBA). Pemphigoid gestationis is confirmed by direct immunofluorescence staining of the biopsy to reveal antibodies. It can be distinguished from BP and EBA using salt split samples of skin. In some cases, circulating antibodies can be detected by a blood test (indirect immunofluorescence test).
Treatment of pemphigoid gestationis
The primary aim of treatment is to relieve itching, prevent blister formation and treat secondary infections. Topical corticosteroids are used in mild disease whilst oral corticosteroids are necessary in more extensive cases. Minimum effective doses should be used to reduce the risk of side effects to both mother and fetus. Oral antihistamines may be used to relieve itching.
Intravenous immunoglobulin has also been reported to be effective. Immunosuppressive medications such as azathioprine or ciclosporin may also be used successfully but their safety in pregnancy or during breast feeding must be carefully considered.
In most cases, pemphigoid gestationis resolves spontaneously within days after delivery so treatment can be tapered off and stopped. Complications are rare but may include:
- Premature delivery
- Transient blistering on the infant that resolves with clearance of maternal antibodies (about 3-4 months)
- Secondary infection, which may leave scarring