SPRY1 and dermatitis: Six weeks after the first tamoxifen induction, almost 100% of Spry1-cKO mice developed arthritis in paws (dactylitis) and psoriasis-like skin inflammation on their ears and paws, while 70% of Spry1-cKO mice showed psoriasis-like dermatitis on the back (Figure 1, A–C, and Supplemental Figure 1G).