Itch in dermatomyositis: the role of increased skin interleukin-31

Summary

Background

Interleukin-31 (IL-31) is implicated in pruritus associated with pruritic skin diseases like atopic dermatitis. Although pruritus is a prominent feature in dermatomyositis (DM), few studies have evaluated the pathogenesis of DM-associated itch.

Objectives

Our goals were to establish the prevalence of itch in DM, and to investigate the role of IL-31 in DM-related itch.

Methods

Pruritus and disease activity of DM were evaluated by a visual analog scale (VAS) and the Cutaneous Disease and Activity Severity Index (CDASI), respectively. Expression of IL-31 and IL-31 receptor alpha (IL-31RA) in lesional DM, non-lesional DM and healthy control (HC) skin was evaluated by qRT-PCR and immunofluorescence. Flow cytometry was performed on skin cells isolated from lesional DM skin to identify cellular sources of IL-31 in DM.

Results

Among 191 DM patients, 50.8% had moderate to severe itch, and itch was correlated with increased cutaneous severity (r= 0.34). In itchy DM patients, gene expression of IL-31 and IL-31RA in lesional skin was upregulated compared to non-lesional skin and HC skin. IL-31 mRNA expression positively correlated with VAS itch score (r= 0.67). On immunofluorescence, immunoreactivity for IL-31 and IL31RA was stronger in lesional skin. Flow cytometry showed lesional DM skin contained significantly more IL-31-producing cells and CD4+ cells were the most common cell type. Lenabasum, an emerging treatment for DM, significantly downregulated IL-31 from CpG-stimulated PBMCs.

Conclusion

Increased skin IL-31 may play a role in DM-associated itch, and ongoing trials will evaluate the effects of systemic treatment on IL-31 and itch in DM.

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