The demonstration of GLUT-1 in IH and the placental syncytiotrophoblast microvilli and basement membranes (17), and the unique co-expression of the placental antigens, merosin, Lewis Y antigen, FCγRIII, and type 3-iodothyronine deiodinase (18–20), has led to the speculation of a placental embolic origin of IH. Here, SLC2A1 is linked to isolated hemihyperplasia.