Additionally, we explored the lactylation scores of different immune cells using single-cell data.<h4>Results</h4>We identified four lactylation-related hub genes (SMARCC2, CCNA2, NUP50, and GATAD2B) highly associated with concurrent RA and AS, which showed high diagnostic potential (area under the curve [AUC] > 0.88). This evidence concerns the gene NUP50 and rheumatoid arthritis.