A 29-Year-Old Woman, Gravida 2 Para 0 Aborta 1, at 34

A 29-year-old woman, gravida 2 para 0 aborta 1, at 34 weeks gestation comes to the office for a routine prenatal visit.  She reports no abdominal pain, leakage of fluid, or vaginal bleeding.  There is normal fetal movement.  Since her last visit 2 weeks ago, she has developed severe pruritus on her abdomen, which has not responded to over-the-counter moisturizers.  The patient has had no recent contact with anyone who has had a fever, rash, or pruritus.  She was diagnosed with gestational diabetes mellitus that is well controlled with an insulin regimen.  Earlier in the pregnancy, she had an episode of vulvar candidiasis that was treated with a topical antifungal.  The patient has no chronic medical problems or previous surgeries.  She takes prenatal vitamins daily and has no allergies.  The patient does not use tobacco, alcohol, or illicit drugs.  Temperature is 36.7 C (98 F) and blood pressure is 100/70 mm Hg.  BMI is 31 kg/m².  Fetal heart rate is 145/min and fundal height is 35 cm.  Physical examination shows prominent abdominal striae and several red linear excoriations on the abdominal wall unrelated to the striae.  Laboratory results are as follows: The patient is prescribed treatment for her symptoms.  She returns a week later for follow-up and reports good fetal movement and no contractions, vaginal bleeding, or leakage of fluid.  Her pruritus has worsened, and blisters have appeared near her umbilicus and are spread out over her abdomen.  Temperature is 36.7 C (98 F) and blood pressure is 100/70 mm Hg.  Fetal heart rate is 145/min and fundal height is unchanged at 35 cm.  Physical examination reveals the following: Which of the following is the most likely diagnosis?

A) Herpes simplex infection
B) Pemphigoid gestationis
C) Primary varicella infection
D) Pruritic folliculitis of pregnancy
E) Pustular psoriasis of pregnancy