Systemic lupus erythematosus (SLE) is an autoimmune disorder characterized by excessive autoantibody production due to B cell hyperactivity. While these immunological SLE features have been primarily observed in Caucasian adult patients, the heterogeneous nature of the disease has made it difficult to understand the disease pathogenic mechanism in-depth. the immunological features of SLE in Asians, particularly the differences between childhood onset SLE (cSLE) and adult onset SLE (aSLE), remain poorly understood. To address this gap, we conducted a study utilizing single-cell RNA sequencing (scRNA-seq) to compare the cellular composition and transcriptional changes in peripheral blood mononuclear cells (PBMCs) from four childhood and four adult SLE patients which treatment naïve. Our comparative analysis identified the composition of B cells, monocytes, NK cells, CD4 T cells and CD8 T cells in aSLE and cSLE PBMCs. We observed an increase in B cells and decrease CD4 T cells in cSLE compared to aSLE. Moreover, we performed sub-clustering of CD4 T cells and B cells to compare differentially expressed genes (DEGs), revealing similar gene expression patterns between the two age groups. Additionally, we observed that in the monocyte population, interferon-stimulated genes (ISGs) including IFI27, IFI44L, IFIT1, ISG15 and SIGLEC1 were more expressed in cSLE compared to aSLE. This finding suggests a potential explanation for why cSLE is generally considered more severe than aSLE. We aim to describe SLE-associated alterations in cellular subsets and transcriptomic profiles within each cell population, along with cytokine expression and cell death processes, stratified by age groups. The findings are expected to provide insights into SLE pathogenesis, contribute to patient stratification strategies, and guide the development of targeted therapeutic approaches.