VDR and osteoporosis: Another study done by Mosaad et al. in Egypt revealed that the vitamin D receptor (VDR) gene polymorphisms (ApaI, TaqI, BsmI, and FokI) might play a role as a risk factor in RA patients for osteoporosis development; the study enrolled 128 RA patients with 150 control subjects and 30 postmenopausal osteoporotic females.