Although striking upregulation of TH17 pathway genes (IL17F and IL36B/G) resembling that seen in patients with psoriasis was common to all patients with ichthyoses in a severity-related manner, patients with Netherton syndrome showed the greatest T-cell activation (inducible costimulator [ICOS]) and a broader immune phenotype with T<sub>H</sub>1/IFN-γ, OASL, and T<sub>H</sub>2/IL-4 receptor/IL-5 skewing, although less than seen in patients with AD (all P < .05).