PTPN22 and autoimmune disease: Among these are well-established common variants (e.g., PTPN22, SH2B3, FUT2), as well as lower frequency hypomorphic alleles (e.g., TYK2, IFIH1) known to be associated with many autoimmune diseases.16 of the associations are low-frequency variants that are highly enriched in Finns (from 4 to more than 100-fold) (Table 1b) − 12 of which are found only in the FinnGen GWAS because of their low frequency in UKBB.