The aim of the European Journal of Rheumatology is to cover various aspects of rheumatology for its readers, encompassing the spectrum of diseases with arthritis, musculoskeletal conditions, autoinflammatory diseases, connective tissue disorders, osteoporosis, translational research, the latest therapies and treatment programs. European Journal of Rheumatology publishes original articles, invited reviews, case based reviews, letters to the editor and images in rheumatology. The publication language of the journal is English.

Objective Juvenile localized scleroderma (LS) is an autoimmune disease of the skin whose pathogenesis is not well understood due to the rarity of the disease. This study was undertaken to determine the skin transcriptome in skin biopsy tissue from children with juvenile LS compared to pediatric healthy controls, with identification of significant molecular targets using RNA sequencing (RNA‐Seq). In this study, differentially expressed genes (DEGs) were assessed for correlations with histopathologic and clinical features in children with juvenile LS, and were used to group the children into distinct genetic clusters based on immunophenotype. Methods RNA‐Seq was performed on sections of paraffin‐embedded skin tissue obtained from 28 children with juvenile LS and 10 pediatric healthy controls. RNA‐Seq was carried out using an Illumina HTS TruSeq RNA Access library prep kit, with data aligned using STAR and data analysis using a DESeq2 platform. A standardized histologic scoring system was used to score skin sections for the severity of inflammation and levels of collagen deposition. Histologic scoring was completed by 2 pathologists who were blinded with regard to the status of each sample. Spearman’s rank correlation coefficients were used to assess significant correlations between DEG expression profiles and skin histologic findings in patients with juvenile LS. Results We identified 589 significant DEGs in children with juvenile LS as compared to healthy controls. Hierarchical clustering was used to demonstrate 3 distinct juvenile LS immunophenotype clusters. The histologic scores of skin inflammation (based on numbers and categories of inflammatory cell infiltrates) were significantly correlated with the expression levels of HLA–DPB1, HLA–DQA2, HLA–DRA, and STAT1 genes (rs > 0.5, P < 0.01). Collagen thickness correlated with the expression levels of collagen organization genes as well as with genes found to be correlated with the severity of inflammation, including genes for major histocompatibility complex (MHC) class I, MHC class II, and interferon‐γ signaling. Conclusion Among children with juvenile LS, 3 distinct genetic signatures, or clusters, were identified. In one cluster, inflammation‐related pathways were up‐regulated, corresponding to the histologic skin inflammation score. In the second cluster, fibrosis‐related pathways were up‐regulated. In the third cluster, gene expression in the skin corresponded to the patterns seen in healthy controls. Up‐regulation of HLA class II genes was observed within the first cluster (characterized by predominant inflammation), a feature that has also been observed in the peripheral blood of patients with morphea and in the skin of patients with systemic sclerosis.