The following is a summary of “Neglected twin: Nummular eczema is a variant of atopic dermatitis with codominant TH2/TH17 immune response,” published in the AUGUST 2023 issue of Allergy & Immunology by Böhner, et al.
Nummular eczema (NE) is a prevalent chronic inflammatory skin condition characterized by pruritic discoid-shaped lesions. Despite its prevalence, the immune mechanisms underlying NE remained incompletely understood, leaving uncertainty about its classification as a variant of atopic dermatitis (AD) or a distinct entity. For a study, researchers sought to compare NE’s clinical, histopathologic, and molecular characteristics with those of type 2 and type 3 skin diseases.
The study conducted bulk RNA sequencing, histologic analysis, and clinical assessments on lesional and nonlesional skin biopsy samples from patients with NE (n = 50), AD (n = 47), and psoriasis (n = 90).
NE exhibited typical features of AD, including compromised epidermal barrier, microbial colonization, spongiosis, and eosinophil infiltration. Additionally, NE displayed aspects reminiscent of psoriasis, such as increased epidermal thickness, Ki-67+ cell count, and neutrophil infiltration. Gene expression analysis revealed upregulation of neutrophil-attracting cytokines (IL19, CXCL8, CXCL5) and comparable expression of TH2-related cytokines (IL13, CCL17, CCL18, CCL26, CCL27) in NE compared to AD. Principal component analysis indicated that AD and NE clustered together, distinct from psoriasis. Furthermore, an established molecular classifier categorized NE as AD rather than psoriasis. Notably, clinical and molecular response to dupilumab treatment was demonstrated in NE.
The study found overlapping type 2 and type 3 immune signatures in NE, predominating type 2 immunity. The findings suggested that type 2 immunity should be the primary focus of targeted therapeutic interventions for NE, supporting the perspective that NE is a variant of AD.