STAT4 and psoriasis: Investigating the genetic polymorphism of STAT4 with autoimmune diseases, many recent studies suggested a significant association of STAT4 gene polymorphism with systemic lupus erythematosus (SLE) [19,20,21,22], rheumatoid arthritis (RA) [23,24,25,26], Crohn’s disease [27,28], Sjögren’s disease (SD) [29], systemic sclerosis [30,31], Behcet’s disease [32,33], and type-1 diabetes (T1D) [34,35,36] as well as psoriasis [37], thus indicating common genetic involvement in multiple autoimmune diseases.