TYK2 and juvenile idiopathic arthritis: Mutations in TKY2 lead to an upregulation of the downstream STAT signaling.632 According to Tomasson et al., G363S mutations were specific for TYK2 proteins in AML.633 Multiple mutations were identified in the TYK2 protein, in nonmalignant diseases such as juvenile idiopathic arthritis, rheumatoid arthritis, inflammatory bowel disease, multiple sclerosis or systematic lupus erythematosus and we will not mention them.634