A case of peeling skin syndrome type 1 with novel <i>CDSN</i> gene variation successfully treated with upadacitinib

Peeling skin syndrome type 1 (PSS1) is an autosomal recessive genodermatosis caused by the CDSN gene loss-of-function mutation and characterized by widespread superficial skin peeling and erythroderma with unbearable pruritus. Because of its ultra-rarity and unclear mechanism, this rare disease has no established treatment regimen. Herein, we reported a Chinese woman who presented with congenital generalized pruritic erythroderma and exfoliation, notable for significantly elevated IgE levels. The whole exome sequencing identified an unpublished homozygous variant (c.295C>T, p.Gln99*) in the CDSN gene, confirming the diagnosis of PSS1. Immunohistochemistry analysis of the affected skin confirmed the lack of corneodesmosin expression, revealed the overexpression of T helper 2 (Th2)-related cytokines harboring interleukin (IL) 4 and IL-13. After Janus kinase 1 (JAK1) inhibitor upadacitinib administration, both the patient's skin rashes and itching symptoms were significantly alleviated. Our work expanded the PSS1-related CDSN gene mutation spectrums, substantiated the hypothesis regarding the overexpression of Th2-related cytokines, and uncovered the important role of JAK1 underlying PSS1. JAK1 signaling may dominate the pathogenesis in PSS1 and represent a potential therapeutic target.