Autosomal recessive congenital ichthyosis (ARCI) is a heterogeneous group of monogenic genodermatoses that encompasses non-syndromic disorders of keratinization. The pathophysiology of ARCI has been linked to a disturbance in epidermal lipid metabolism that impaired the stratum corneum function, leading to permeability barrier defects. Functional characterization of some genes involved in ARCI contributed to the identification of molecular actors involved in epidermal lipid synthesis, transport or processing. Recently, PNPLA1 has been identified as a gene causing ARCI. While other members of PNPLA family are key elements in lipid metabolism, the function of PNPLA1 remained unclear. We identified 5 novel PNPLA1 mutations in ARCI patients, mainly localized in the putative active enzymatic domain of PNPLA1. To investigate Pnpla1 biological role, we analysed Pnpla1-deficient mice. KO mice died soon after birth from severe epidermal permeability defects. Pnpla1-deficient skin presented an important impairment in the composition and organization of the epidermal lipids. Quantification of epidermal ceramide species highlighted a blockade in the production of ω-O-acylceramides with a concomitant accumulation of their precursors in the KO. The virtually loss of ω-O-acylceramides in the stratum corneum was linked to a defective lipid coverage of the resistant pericellular shell encapsulating corneocytes, the so-called cornified envelope, and most probably disorganized the extracellular lipid matrix. Finally, these defects in ω-O-acylceramides synthesis and cornified envelope formation were also evidenced in the stratum corneum from PNPLA1-mutated patients. Overall, our data support that PNPLA1/Pnpla1 is a key player in the formation of ω-O-acylceramide, a crucial process for the epidermal permeability barrier function.

JEADV AbstractBackground Three biotherapiesetanercept, adalimumab and ustekinumabare licensed in childhood psoriasis. The few data available on their efficacy and tolerance are mainly derived from industry trials. However, biological drug survival impacts long-term performance in real-life settings.Objective The objective of this study was to evaluate the survival rates of biological therapies in children with psoriasis in real-life conditions. Secondary objectives were to evaluate the factors associated with the choice of the biological therapy and to report severe adverse events. Materials and methodsThis study was an observational retrospective study. Data were extracted from the clinical records of 134 children. Kaplan-Meier estimates were used to analyse drug survival overall and in subgroups of plaque psoriasis, bio-na€ ıve and non-na€ ıve patients. ResultsWe analysed 184 treatment courses: 70 with etanercept, 68 with adalimumab and 46 with ustekinumab.Factors associated with the choice of first-line biological agent were age at initiation (younger for adalimumab, P < 0.0001), age at onset of psoriasis (younger for adalimumab and etanercept, P = 0.03) and baseline Psoriasis Assessment Severity Index and Physician global assessment (both higher for adalimumab, P < 0.001). Drug survival rates were higher for ustekinumab than for adalimumab and etanercept (P < 0.0001) for all treatment and all psoriasis types, plaque-type psoriasis (P = 0.0003), patients na€ ıve for biological agents (P = 0.0007) and non-na€ ıve patients (P = 0.007). We reported eight serious adverse events (SAEs): severe infections (n = 3), significant weight gain (n = 2), psoriasis flare (n = 1) and malaise (n = 1). Biological therapy was discontinued in three children (one with psoriasis flare and two with weight gain). Only the two cases of weight gain resulted in an unfavourable outcome.Conclusions Our real-life comparative study found that ustekinumab had the best drug survival outcome. The profile of SAEs in children was comparable to that in adults. These results will assist dermatologists in the decision-making process when choosing treatment options for children with psoriasis in daily practice.