LCT and rheumatoid arthritis: The four PCs associated with RA status in the subsets that removed the MHC region and the chromosome 8 inversion, (S3 and S4), or filtered out SNPs in high LD (S5 and S6) exhibited minimal extreme SNP weights across the genome other than a small region on chromosome 2 that contains the lactase gene (LCT), which is known for strong structure in European populations [17].