Synovial immunopathology in psoriatic arthritis: cellular and molecular insights.

Although psoriatic arthritis and rheumatoid arthritis are both common types of inflammatory arthritis characterised by synovial inflammation, there are distinct molecular and cellular landscapes between these conditions. Recent advances in synovial research in psoriatic arthritis have begun to unlock important insights into disease pathogenesis and potential clinical applications. For example, studies using high-dimensional technologies have identified psoriatic arthritis-specific macrophage, fibroblast, and mast cell subsets, as well as specific cytokines, such as IL-36 and IL-41, that drive pathogenesis. This Review explores how research of the synovium has advanced the understanding of psoriatic arthritis, the potential of identified cell types and cytokines as biomarkers and novel therapeutic targets, how limited sample sizes in high-dimensional studies are hindering clinical translation, and the future directions for synovial research in psoriatic arthritis.