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Pemphigoid gestationis (PG) is an autoimmune bullous disease of pregnancy, characterised by deposition of complement (and sometimes immunoglobulin) in the lamina lucida of the cutaneous basement membrane. It was, rather confusingly, named herpes gestationis because the blisters had herpetiform features. However, there is no connection with herpes virus infection.
Patients develop circulating antibodies of the immunoglobulin G1 subclass which bind to basement membrane and trigger an immune response causing subepidermal vesicles and blisters. There is antigenic overlap with the antibodies of bullous pemphigoid. The trigger for development of auto-antibodies is unknown but cross-reactivity between placenta and skin may play a role.
PG is very rare and affects only about 1 person in 50,000-2 million pregnancies (depending on HLA type prevalence). The association with HLA-DR3 and HLA-DR4 haplotypes is reflected in a higher incidence in Caucasians.
- Lesions may appear at any time during pregnancy but they most commonly develop during the second and third trimesters.
- There is sudden onset of extremely pruritic urticarial papules and blisters on the abdomen and trunk. Pruritus is severe and unrelenting.
- Lesions start with erythematous urticarial patches and plaques around the umbilicus. They progress to tense vesicles and blisters. Sometimes urticarial plaques may never develop blisters. They differ from true urticaria because they are relatively fixed in nature.
- The rash spreads peripherally, often sparing the face, palms and soles. Mucosal lesions occur in fewer than 20% of cases.
- Symptoms remit in the weeks before delivery in 75% but dramatic flares can occur immediately postpartum.
- It usually resolves within weeks to months after delivery and possibly more quickly with breast-feeding. Disease persisting for years after delivery has been reported.
- It may recur with the resumption of menstruation, use of oral contraception and with subsequent pregnancies.
It is an uncommon condition and shares some features with other skin diseases of pregnancy. As a result, diagnosis can be difficult.
- Bullous pemphigoid.
- Cicatricial pemphigoid.
- Pruritic urticarial papules and plaques of pregnancy (PUPPP).
- Linear IgA dermatosis.
- Dermatitis herpetiformis.
- Erythema multiforme.
- Papular dermatitis of pregnancy.
- Pruritic folliculitis of pregnancy.
- The characteristic clinical presentation.
- Characteristic histology (subepidermal blistering).
- Direct immunofluorescence (DIF) tests.
- Indirect immunofluorescence (IDIF) tests.
- HLA testing (45% have HLA-DR3, HLA-DR4 compared with 3% of the general population).
The DIF test is important but gives similar results in bullous pemphigoid and epidermolysis bullosa acquisita.
PG has been described in association with hydatiform mole or choriocarcinoma. Affected patients are more likely to develop other autoimmune diseases - for example, Hashimoto's thyroiditis and pernicious anaemia.
Oral corticosteroids are safe and are the mainstay of treatment in pregnancy and postpartum. Prednisolone is usually started at a dose of 0.5-1 mg/kg/day. Antihistamines are also used. Plasmapheresis and immunophoresis have been used in difficult-to-treat cases.
Shared care involving obstetrician, dermatologist and paediatrician is appropriate.
- Premature labour in 20%.
- Lifetime risk of autoimmune disease.
There is no increased maternal or child mortality.
- There is a greater prevalence of premature or small-for-dates babies.
- 5-10% of infants may have transient cutaneous involvement that clears as the maternal antibodies wane.
- Patients are more susceptible to other autoimmune diseases, including Hashimoto's thyroiditis, Graves' disease and pernicious anaemia.
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Further reading & references
- Pemphigoid gestationis; DermNet NZ
- Savervall C, Sand FL, Thomsen SF; Dermatological Diseases Associated with Pregnancy: Pemphigoid Gestationis, Polymorphic Eruption of Pregnancy, Intrahepatic Cholestasis of Pregnancy, and Atopic Eruption of Pregnancy. Dermatol Res Pract. 2015 2015:979635. doi: 10.1155/2015/979635. Epub 2015 Nov 2.
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