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Nummular Eczema: A Variant of Atopic Dermatitis With Dual Immune Response
According to a recent study published in the Journal of Allergy and Clinical Immunology shedding light on the underlying immune mechanisms of nummular eczema (NE), researchers have revealed that this common chronic inflammatory skin disease exhibits a dual immune response, with features resembling both atopic dermatitis (AD) and psoriasis. This research raises important questions about the classification of NE and has significant implications for targeted therapeutic interventions.
The researchers aimed to compare the clinical, histopathologic, and molecular characteristics of NE with those of type 2 and type 3 skin diseases. To achieve this, the research team conducted bulk RNA sequencing, along with histologic and clinical studies, using lesional and nonlesional skin biopsy specimens from patients with NE, AD, and psoriasis.
The findings unveiled intriguing similarities and distinctions between NE and other skin diseases. NE displayed typical hallmarks of AD, such as an impaired epidermal barrier, microbial colonization, spongiosis, and eosinophil infiltration. However, the study also found aspects of psoriasis in NE, including increased epidermal thickness, the number of Ki-67+ cells, and neutrophilic infiltration. At the gene expression level, NE demonstrated an upregulation of neutrophil-attracting cytokines (IL19, CXCL8, CXCL5) and expression of TH2-related cytokines (IL13, CCL17, CCL18, CCL26, CCL27) similar to those observed in AD. Importantly, principal component analysis of transcriptome data from lesional skin revealed that AD and NE clustered together, distinctly different from psoriasis. Furthermore, an established molecular classifier identified NE as AD rather than psoriasis.
The study also demonstrated the clinical and molecular efficacy of dupilumab treatment in NE, reinforcing the view of NE as a variant of AD. These results underscore the importance of targeting type 2 immunity in specific therapeutic interventions for NE, given its predominance in the disease's immune response.
“NE shows overlapping type 2 and type 3 immune signatures, while type 2 immunity predominates and should be the primary target of specific therapeutic interventions,” concluded the study authors. “This supports the view of NE as a variant of AD.”
Reference
Böhner A, Jargosch M, Müller NS, et al. The neglected twin: nummular eczema is a variant of atopic dermatitis with codominant TH2/TH17 immune response. J Allergy Clin Immunol. 2023;S0091-6749(23)00514-6. doi:10.1016/j.jaci.2023.04.009
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