A study conducted in Sweden in which 3093 subjects took part, of which 1419 had RA, had the following conclusions: RA and T1DM are associated, this association was specific for patients with positive ACPA, and the risk of developing a T1DM in patients with RA could be partially attributed to the presence of the 620W PTPN22 allele, which may represent a common pathway in the pathogenesis of the two diagnoses [93]. This evidence concerns the gene PTPN22 and type 1 diabetes mellitus.