Luo S, Clarke SLN, Ramanan AV, et al. - Researchers conducted two‐sample Mendelian randomization (MR) study to determine the role of platelet glycoprotein Ib α‐chain (GPIbα) plasma protein levels in cardiovascular, autoimmune, and autoinflammatory diseases and whether its impacts are mediated by platelet count. Utilizing two‐step MR and multiple‐trait colocalization approaches, the authors provide valid genetic evidence that genetic variants that regulate GPIbα proteomic pathways, which have a well‐characterized biology function on platelet count, play a causal etiologic role in oligoarticular and RF‐negative polyarticular JIA. The results point to platelets' active role in these JIA subtypes, as well as GPIbα as a putative therapeutic target for these JIA subtypes.