Multiple dermal fibroblasts in patients with pruritic urticarial papules and plaques of pregnancy. A clue to the etiology?

We have recently demonstrated that in pruritic urticarial papules and plaques of pregnancy (PUPPP) there are multiple dermal fibroblasts with no deposition of mucin. We suggest that in the dermis of patients with PUPPP there is a deposition of a substance that induces fibroblasts proliferation. We assume that this substance (marked as F-substance) is a product of the placenta, which is released to the maternal circulation during pregnancy.