TYK2 and ulcerative colitis: Tyrosine kinase 2 (TYK2) was identified as a Ps risk gene in 2010 [4,5], with its genetic variation associated with several other autoimmune diseases, including multiple sclerosis, systemic sclerosis, Type 1 diabetes, Crohn’s disease, ulcerative colitis, and systemic lupus erythematosus [6].