Itch and Janus Kinase Inhibitors

Itch is a common skin symptom, with complex aetiology and pathogenesis. It is mediated by 2 pathways, the histaminergic and non-histaminergic pathways. Chronic itch is understood to be processed by the latter and is difficult to treat with traditional pruritus therapies. The Janus kinase and signal transducer and activator of transcription pathway is a signalling mechanism that regulates gene expression through various cytokines. Janus kinase inhibitors, which have been tested and used for several autoimmune diseases, have also been shown to be effective for itch through clinical trials and case reports. Janus kinase inhibitors could be a good choice for pruritus in atopic dermatitis, psoriasis, and other diseases, such as prurigo nodularis and lichen planus, with rapid itch relief compared with conventional treatments. The most common adverse effects reported include nasopharyngitis, acne, and elevated blood creatine phosphokinase levels. Janus kinase inhibitors are currently prescribed with warnings about a potential increase in malignancies and cardiovascular diseases and usage in people of older ages. This review aims to provide knowledge about itch and the Janus kinase and signal transducer and activator of transcription pathway and to analyse the current evidence for itch relief by Janus kinase inhibitors. SIGNIFICANCE Many patients report itch during dermatology examinations. Chronic itch is defined as itch lasting for more than 6 weeks and is often resistant to conventional treatments. Several inflammatory diseases are mediated by the Janus kinase and signal transducer and activator of transcription pathway, a signalling mechanism that controls gene expression. Recently, clinical trials and cases have reported that inhibitors of this pathway could reduce itch rapidly and effectively. This paper reviews the pathophysiology of itch and analyses the efficacy and safety of Janus kinase inhibitors for itch reduction in various dermatological diseases, including atopic dermatitis and psoriasis, as well as prurigo nodularis and chronic pruritus of unknown origin.