Track

Basic Science

Abstract

Differentiating cutaneous lupus erythematosus (CLE) from its mimickers can present a diagnostic challenge due to its varied clinical and histopathologic features. CD123 immunohistochemistry is used to highlight plasmacytoid dendritic cells (PDCs) in CLE to assist in diagnosis, though its utility can be limited in biopsies with sparse dermis. RNA in situ hybridization (RISH), which has demonstrated efficacy in inflammatory dermatoses like psoriasis and atopic dermatitis as a diagnostic adjunct, has not yet been evaluated in CLE. Here we sought to identify and validate reliable markers for CLE by using RISH. Analysis of previously published gene expression data identified ISG15 and IFI6, which are highly expressed in CLE. RISH for ISG15 and IFI6 was performed on samples from 11 CLE patients, 8 healthy controls, and 11 patients with other inflammatory dermatoses. Two blinded dermatopathologists scored staining intensity in the epidermis and dermis using a semi-quantitative system. CLE samples demonstrated strong and diffuse staining for ISG15 and IFI6, compared to minimal staining in controls and sparser staining in psoriasis, lichen planus, and atopic dermatitis. Basal epidermal staining with superficial and deep involvement clearly distinguished CLE from other inflammatory dermatoses. Compared to CD123, which was positive in 6 of 7 tested cases of CLE, RISH provided broader tissue involvement with high staining intensity, and may offer clearer distinction from mimics. These findings suggest that ISG15 and IFI6 RISH may serve as a useful test for diagnosing CLE. Future studies should evaluate these markers across additional diseases to optimize clinical utility.