Pemphigoid gestationis appears to be an autoimmune phenomenon, probably caused by an IgG antibody to a 180-kD antigen in the basement membrane zone of the epidermis. Although previously called herpes gestationis (because the rash resembles the vesicobullous rash due to herpes simplex virus infection), this disorder is not caused by herpesvirus.
Pemphigoid gestationis occurs in 1/2,000 to 50,000 pregnancies; it usually begins during the 2nd or 3rd trimester but may begin during the 1st trimester or immediately postpartum. It usually recurs with subsequent pregnancies and occurs after oral contraceptive use in about 25% of women. Flare-ups are common 24 to 48 hours postpartum and can occur during subsequent menses or ovulation.
Most fetuses are unaffected; however, transient lesions occur in < 5% of neonates born to mothers with pemphigoid gestationis. Risks, including infant mortality, are increased after premature delivery and in infants who are small for gestational age.
The rash is very pruritic. Lesions often start around the umbilicus, then become widespread. Vesicles and bullae are the most specific lesions; erythematous plaques may develop. The palms, soles, trunk, buttocks, and extremities may be affected but usually not the face or mucous membranes.
The rash worsens during labor or immediately postpartum in up to 75% of women, typically remitting within a few weeks or months.
Neonates may have erythematous plaques or vesicles that resolve spontaneously in a few weeks.
Pemphigoid gestationis may be confused clinically with several other pruritic eruptions of pregnancy, particularly pruritic urticarial papules and plaques of pregnancy. Pemphigoid gestationis can often be distinguished because it usually begins in the periumbilical area; pruritic urticarial papules and plaques of pregnancy usually begin in the striae.
Direct immunofluorescence examination of perilesional skin is diagnostic. It detects a linear band of C3 at the basement membrane zone.
Because fetal risks are increased, prenatal testing (eg, nonstress testing) is recommended.
For mild symptoms, topical corticosteroids (eg, 0.1% triamcinolone acetonide cream up to 6 times a day) may be effective. Prednisone (eg, 40 mg orally once a day) relieves moderate or severe pruritus and prevents new lesions; dose is tapered until few new lesions erupt, but it may need to be increased if symptoms become more severe (eg, during labor). Systemic corticosteroids given late in pregnancy and in short bursts, do not seem to harm the fetus.
Nonsedating oral antihistamines can also be used to relieve pruritus.
Pemphigoid gestationis probably has an autoimmune etiology; it is not caused by herpesvirus, even though the rash resembles the vesicobullous rash due to herpes simplex virus infection.
Most fetuses are unaffected.
Try to differentiate the rash based on clinical criteria (eg, its initial appearance in the periumbilical area).
Treat women with topical corticosteroids or, if symptoms are severe, oral corticosteroids.