For the expression, the data are consistent with these observations as MR-based causal inference showed that the expression of PTPN22 in the blood was negatively associated with the lifespan (−0.51 year per 1 SD, Pcausal = 2.08 × 10−5) and positively associated with the risk of RA (per 1 SD odds ratio (OR): 2.62, 95% CI: 2.25–3.06, Pcausal = 3.37 × 10−9) (Fig. 6c). Here, PTPN22 is linked to rheumatoid arthritis.