A pregnant woman presents with a generalised symmetrical rash of blisters and serous crusts. What is the cause?
A 26-year-old pregnant woman developed a symmetrical intensely pruritic eruption that commenced around her umbilicus and became generalised in the third trimester. Grouped and annularly distributed blisters were present which broke to produce serous crusts. Skin biopsy revealed an intense subepidermal oedema with blister formation and a mixed inflammatory reaction consisting of lymphocytes and eosinophils. Immunofluorescence of the skin for the presence of antibodies revealed the presence of linear deposits of IgG and complement along the basement membrane zone.