DHCR7 and type 1 diabetes mellitus: On the other hand, a significant relation between SNPs in the CYP2R1, DHCR7 (NADSYN1) and CYP27B1 genes and predisposition to type 1 diabetes have been reported [45], and genetic polymorphisms in the vitamin D system may be more important in the pathogenesis of autoimmune diseases than in the diseases studied by us.