By Gary M. White, MD
Pemphigoid gestationis (PG) is an autoimmune blistering disorder most commonly associated with pregnancy although it may occur in association with trophoblastic tumors, hydatidiform mole or choriocarcinoma. PG binds the NC16A domain of collagen XVII (BPAG2, BP180). In a series of 87 patients, the average age was 28 years and the onset ranged from 5 weeks gestation to 35 days postpartum. 18% presented in the first trimester, 34% in the second, 34% in the third and 14% presented postpartum. In that same review, there was no association with change in male partner as previously suggested.
Itching is often the first symptom. The skin lesions of PG often begin on the abdomen and include urticarial plaques, vesicles and frank bulla. It may then spread to the rest of the trunk and extremities, but is rare on the face or oral mucosa. Flares have been noted after delivery, with the resumption of menses, ovulation or beginning oral contraceptives. Approximately 20% of patients will experience premature delivery. Up to 10% of the babies will develop skin lesions due to passive transfer of antibodies. Approximately 10% of patients will develop Graves disease.
DIF of perilesional skin shows linear deposition of C3 along the basement membrane zone. Alternatively CD4 immunohistochemistry of Formalin fixed tissue is positive in PG and negative in PUPPP. Enzyme-linked immunosorbent assay (ELISA) detects the specific antibodies (usually IgG4) against collagen XVII.
BP180 ELISA is a valuable test to differentiate PG from PUPPP as it is highly sensitive for PG, negative in PUPPP and is unaffected by the use of topical steroids which can cause a skin biopsy DIF to give a false negative result [JAAD 2017;76;560].
Antihistamines (e.g. chlorpheniramine) and potent topical steroids (beginning for example with triamcinolone 0.1% ointment BID and increasing as needed) should be tried initially. However, in a large study, 80% of patients required systemic steroids. Prednisone may be given, e.g. 40 mg/d initially, then tapered as appropriate. The dose may be increased in anticipation of a post-partum flare. Use of systemic corticosteroids does not appear to increase fetal risk, and may actually decrease it due to reduction of placental inflammation [BJD 2009;160:1222–8]. PG typically resolves after the postpartum period. PG tends to recur in subsequent pregnancies with a trend toward increased severity and earlier onset. Rarely, the patient may go on to develop typical bullous pemphigoid.
A case is reported of a woman with severe recurrent PG leading to miscarraige, presenting with detectable circulating autoantibodies at the beginning of pregnancy who was given rituximab to prevent PG with a successful outcome for both mother and baby [JEADV 2017;31;e206]. Of note, rituximab is generally not recommended in pregnancy.
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