PTPN22 and atrial fibrillation: When subgrouping patients according to the type of onset of disease, we observed the significant association of the PTPN22 rs2476601 risk allele A only in patients with ITO (AF 13%, OR 1.63, n = 232, p = 0.016), but not in those without ITO (AF 9%), compared to healthy controls (AF 8%).