CYP1A1 and psoriasis: On the other hand, CYP1A1 mRNA expression, a biomarker of AHR activation, is reported to be increased in lesional psoriasis compared to healthy skin in two small studies performed in Korea [105,106], while it is decreased in Zhu et al.’s [109] and in our own study [104], both performed in predominantly White cohorts, as well as in another study performed in Korea (Table 1).