Tregs of patients with severe psoriasis, compared to healthy controls, have an enhanced propensity to differentiate into IL-17A-producing cells on ex vivo stimulationTreg differentiation was linked to unexpectedly high RORγt levels and enhanced loss of Foxp3.IL-23 boosted Treg differentiation in psoriasis patients but less in controlsIL-23 further reduced Foxp3 expression while leaving high RORγt levels unaffected. This evidence concerns the gene IL23A and psoriasis.