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Uncommon pregnancy-associated autoimmune bullous dermatosis
- Pemphigoid gestationis (PG) is a rare dermatopathic autoimmune-mediated, self-limited eruption most often occurring during midpregnancy. It most commonly involves the periumbilical region.
- Most commonly begins in 2nd or 3rd trimester of pregnancy, waning just prior to delivery and then flaring after delivery; can occur at any time in pregnancy and postpartum period
- Often recurs in subsequent pregnancies (likely earlier onset and more severe) (1)
- Characterized by intense pruritus followed by polymorphous papules and vesicles that coalesce into bullae
- Often periumbilical or with other truncal foci
- May also affect the buttocks, forearms, palms and/or soles
- Less frequently, scalp and face are involved.
- Mucous membranes are typically spared, but intestinal mucosa may have celiac-like lesions without significant clinical malabsorption.
- Pruritus may precede lesions by days to weeks.
- System(s) affected: immune; skin; reproductive
- Synonym(s): herpes gestationis; dermatitis gestationis
- Rare: ~1/50,000 pregnancies
- Varies by HLA-DR3 and HLA-DR4
- Predominant age: childbearing years
- Predominant sex: female
- ~5–10% of infants born to mothers with PG have cutaneous lesions that are usually self-limited and likely the result of transplacental passage of maternal IgG antibasement membrane zone autoantibodies.
- Children born to mothers with PG are not at increased risk of autoimmune diseases.
- By definition, PG is a condition of pregnancy and puerperium; rarely seen in conjunction with hydatidiform mole and choriocarcinoma
- Fetuses of mothers with PG are at risk for growth restriction and prematurity due to potential placental insufficiency (immune response to placental antigens). Stillbirth is less common. Antenatal testing is indicated.
- Treatment with systemic corticosteroids does not adversely affect pregnancy outcomes (2).
- With each subsequent pregnancy, disease can recur with earlier onset. It is possible that subsequent pregnancies are unaffected as well.
Etiology and Pathophysiology
During pregnancy, patients develop IgG autoantibodies to placental proteins that cross-react with the same proteins in maternal skin (and potentially fetus) (3).
- Primary antigen is BP180 (type XVII collagen or BPAG2; a transmembrane protein required for dermal-epidermal adhesion); less frequent antigen is BP230.
- Maternal IgG autoantibodies are presented to maternal immune system by aberrantly expressed HLA class II major histocompatibility complex (MHC II) on amniochorionic stromal cells and trophoblasts.
- Maternal antiplacental IgG antibodies cross-react with BP180 in the skin.
- Autoantibodies initiate complement 3 (C3) fixation, complement and leukocyte activation, which release proteolytic enzymes that separate the dermis and epidermis forming vesicles and bullae.
- Higher association with HLA-DR3 and HLA-DR4
- Not caused by herpesvirus
Genetic predisposition is possible given HLA-DR3 and HLA-DR4 association.
- Episode in prior pregnancy
- Herpes simplex does not increase risk.
- Avoid secondary infection of open skin lesions.
- Estrogens may trigger future flare-up (e.g., oral contraceptives and menses).
Commonly Associated Conditions
- Rarely, trophoblastic tumors, hydatidiform mole, and choriocarcinoma
- Other autoimmune diseases (e.g., thyroid disorders including Graves disease, pernicious anemia)