Association of vitamin D receptor genotypes with early onset rheumatoid arthritis

The presence of certain vitamin D receptor (VDR) genotypes has been associa ted with low bone mineral density (BMD) in elderly populations as well as w ith accelerated bone loss in patients with rheumatoid arthritis (RA). In th e present study, VDR genotypes from 120 Spanish patients with RA were inves tigated. Three VDR gene polymorphisms (BsmI, ApaI and TaqI) were investigat ed using polymerase chain reaction followed by enzymatic digestion. The dis tributions of VDR allelic frequencies were similar in patients and controls and therefore no influence of VDR polymorphisms on rheumatoid arthritis su sceptibility could be demonstrated. However, in an analysis of the clinical features of the different VDR-related genetic subgroups, the BB/tt genotyp e, defined by the BsmI and TaqI restriction site polymorphisms, was identif ied to be weakly associated with an early onset RA in female patients. This VDR genotype has been associated with a low BMD level in various studies. When patients were stratified according eo the presence of the shared HLA e pitope SE, it was found that SE + female patients bearing the BB/tt genotyp e showed the earliest disease onset. The mechanisms by which the VDR polymo rphism is associated with RA is unknown, but they could be related to the i mmunoregulatory properties of vitamin D.