However, PASI was significantly correlated with neither IL-17A nor Claudin-1 in psoriasis (r = − 0.199, p = 0.202; r = − 0.026, p = 0.867, respectively), in early-onset psoriasis (r = − 0.181, p = 0.339; r = 0.141, p = 0.451, respectively), in late-onset psoriasis (r = − 0.355, p = 0.257; r = − 0.026, p = 0.526, respectively), in mild psoriasis (r = − 0.464, p = 0.060; r = − 0.350, p = 0.169, respectively) and in moderate-to-severe psoriasis (r = − 0.322, p = 0.109; r = 0.174, p = 0.395, respectively) in Figure 2 and Supplementary Table 4. Here, CLDN1 is linked to psoriasis.