Gestational dermatosis shortly after implantation associated with parental class II HLA compatibility and maternal immune activation: Preliminary report of a prospective case series

Background: Pregnancy represents a semiallograft, subject to similar immune responses as allogeneic organ transplants. Tolerance of pregnancy appears best with maximal class II HLA heterogeneity between mother and father, while compatibilities are associated with increased pregnancy loss and maternal autoimmunity. Tolerance abnormalities often involve skin reactions. Abnormalities in tolerance of the fetal graft may do the same. Objective: To define the characteristics of a newly described dermatosis in very early pregnancy. Methods: Prospective case series of 7 couples/12 clinical episodes. Results: The dermatosis was observed in 7 out of 285 women undergoing in vitro fertilization (IVF; 2.5%; 95% CI 0.66-4.26%) and in 12 out of 277 total IVF cycles reaching embryo transfer (4.3%; 95% CI 1.93-6.73%). Prior to IVF all women reported autoimmune clinically significant allergies. All but 1 couple demonstrated class II HLA compatibility. Two of 4 pregnancies miscarried. All rashes erupted within days from embryo implantation. Conclusions: The 'implantation rash' reported here is uncommon but not rare. It may be the consequence of abnormal maternal immune responses to embryo implantation in women with prior immune activation, associated with class II HLA compatibility between parents. Further prospective studies are required to better define this condition.