Most critical pharmacogenomic variant causing complete loss of DPD enzyme function; increases fatal 5-FU/capecitabine toxicity risk without dose reduction

Intronic PTPN1 tag SNP raising LDL cholesterol risk in lean individuals

Reduces intestinal GCPII enzyme activity by 53%, paradoxically raising circulating folate

17q21 regulatory variant in the IKZF3-ORMDL3-GSDMB locus with opposite effects — risk for autoimmune diseases (RA, Crohn's, Graves') but protective for asthma

Tag SNP for HLA-DRB5*01:01 on the DR15 susceptibility haplotype, physically near HLA-DRB5 in the MHC region and in near-complete LD with rs3135388; the DRB5*01:01 allele contributes independently to multiple sclerosis and narcolepsy risk by presenting myelin and viral peptides to autoreactive CD4+ T cells

Phase II glucuronidation enzyme that metabolizes bilirubin and many drugs including irinotecan; reduced activity causes Gilbert syndrome and severe chemotherapy toxicity

Pleiotropic 12q24 locus variant in SH2B3 (LNK) modulating JAK-STAT cytokine signaling, with associations spanning blood pressure, celiac disease, and coronary artery disease

Phosphatidylcholine production — affects dietary choline requirements

Tag SNP for HLA-DRB1*15:01 (physically located near HLA-DRA), the strongest genetic risk factor for multiple sclerosis, with implications for vitamin D optimization and EBV immune control

Intronic variant in STAT6 (intron 2) that creates an NF-κB binding site, increasing STAT6 promoter activity; the T allele is associated with elevated total serum IgE and increased risk for atopic dermatitis and allergic rhinitis through enhanced Th2 signaling