TYK2 and rheumatoid arthritis: For example, IL23R is known to be associated with AS-related diseases including IBD80 and psoriasis.81 Variants in TYK2 are associated with AS, IBD, psoriasis, type 1 diabetes, multiple sclerosis and rheumatoid arthritis.82 Multiple genes related with IL23R pathway are shared between IBD and AS, including IL23R, IL12B, TYK2, JAK2, IL27 and CARD9, highlighting that the two diseases probably share similar aetiology through IL-23R pathway.29