Objective In this study, we aimed to screen 31 genes (C1QA, C1QB, C1QC, C1R, C1S, C2, C3, TREX1, RNASEH2A, RNASEH2B, RNASEH2C, SAMHD1, ADAR, DNASE1, DNASE1L3, PRKCD, ACP5, SLC7A7, IFIH1, TMEM173, ISG15, CYBB, FAS, FASLG, KRAS, NRAS, MAN2B1, PEPD, PTPN11, RAG2, and SHOC2), that we have categorized under the umbrella term “monogenic lupus” using a targeted next-generation sequencing (NGS) panel in 24 individuals with early-onset (≤10 years of age) systemic lupus erythematosus (SLE) and in 24 patients with late-onset (>10 years of age) disease. Methods A total of 48 SLE patients (24 with disease onset ≤10 years of age and 24 with disease onset >10 years of age) were included. Patients with late-onset disease have been used as patient controls. Sequencing was carried out using 400 bp kit on the Ion S5 system. Results Among the 48 patients, three had one pathogenic variant and 45 patients had at least one rare variant classified as benign, likely benign or variant of unknown significance (VUS). In all three patients with a pathogenic variant, the onset of disease was before 10 years of age. Two patients (they were siblings) carried C1QA homozygote pathogenic allele (p.Gln208Ter, rs121909581), and one patient carried PEPD heterozygote pathogenic allele (p.Arg184Gln, rs121917722). Conclusion We demonstrated a pathogenic variant in our target gene panel with a frequency of 9.52% in patients with a disease onset ≤10 years of age. All patients with early-onset SLE phenotype, irrespective of a positive family history for SLE or parental consanguinity, should be scanned for a single-gene defect by a targeted gene panel sequencing. With the discovery of many single-gene defects and ongoing efforts to identify novel genes in SLE, similar gene panels including even more genes will possibly become more necessary and practical in the future.
