Blocking of IL‐4/IL‐13 Signalling With Dupilumab Results in Restoration of Serum and Cutaneous Abnormalities in Netherton Syndrome

ABSTRACT Netherton syndrome (NS) is a rare ichthyosis caused by SPINK5‐ null mutations, resulting in erythroderma, ichthyosis linearis circumflexa, and atopic diathesis. Elevated serum IgE levels and activation of the KLK5‐PAR2‐TSLP axis suggest involvement of Th2‐skewed immunity in NS. In this pilot study, we investigated the effects of IL‐4/IL‐13 blocking with dupilumab on NS features. At baseline, Th2‐chemokines CCL11, CCL17, CCL18, CCL26, and serum IgE were more elevated in atopic dermatitis (AD) than in NS vs. controls (ctrls). AD exhibited elevated serum levels of CCL27, LDH, and eosinophils, while NS showed higher levels of IL‐9 and IL‐18. Epidermal aberrations, including acanthosis and SC‐detachment, were present in NS versus ctrls. The number of CD3+ T cells increased, while CD1a + Langerhans cell numbers decreased in NS skin. Amounts of KLK5 were reduced, and the distribution of KLK7 was abnormal in NS epidermis as compared to ctrls. Reduced amounts of FLG, CDSN, and DSG1 highlight impaired keratinocyte late differentiation in NS. Amounts of epidermal TSLP were diminished. Upon dupilumab treatment, clinical improvement in NS began as early as week 8 and continued up to 30 months, with no serious side effects reported. Serum levels of IgE, CCL17, CCL26, IFN‐γ and IL‐18 decreased upon IL‐4/IL‐13 blockade, and alterations of cutaneous immune cells improved in NS. Furthermore, the epidermal protease inhibitor WFDC12 expression increased after dupilumab treatment, concurring with improved and partially normalised epidermal structure, including increased FLG, CDSN, and DSG1. These data highlight Th2‐skewed immunity in NS and emphasise the amelioration of NS features through dupilumab treatment.