Primary sclerosing cholangitis: a narrative review of diagnostic and prognostic biomarkers.

Background and Objective: Primary sclerosing cholangitis (PSC) is an autoimmune biliary fibrosing disease characterized by inflammation and injury of the intra- and/or extrahepatic bile ducts. The pathogenesis of PSC is poorly understood but is believed to be multifactorial, involving genetic predisposition, immunological dysregulation, and environmental influences. These may include disturbances in the gut-liver axis such as immune dysfunction in the colon and liver, alterations in the fecal and biliary microbiome, conjugation of bile acids into toxic species, and compromised intestinal epithelial integrity due to colitis, resulting in translocation of bacterial byproducts to the liver. There is a critical need for diagnostic and prognostic biomarkers that would enhance management and outcomes for patients with PSC. Additionally, validation of such biomarkers could serve as measurable endpoints when conducting future clinical trials. This aim of this paper is to review the available literature on candidate diagnostic and prognostic biomarkers in the adult and pediatric PSC populations. Methods: Original studies investigating biomarkers in serum, bile, and tissue published until November 2024 were systematically searched on PubMed, with a specific focus on newer studies published in the past 10 years and pediatric studies. Small studies with fewer than 10 patients in each study group, animal model studies, and studies with a focus on biomarkers for cholangiocarcinoma were excluded. Key Content and Findings: Diagnostic and prognostic biomarkers summarized in this review include autoantibodies, markers of innate and adaptive immune responses, extracellular vesicles, epigenetic modifications, microbiome, proteins involved in lipid metabolism and bile acid homeostasis, and markers of fibrogenesis. Novel concepts for future biomarker discovery and implementation, including the potential for insights to be gained from the pediatric PSC population, are explored. Conclusions: There is a critical need for further biomarker discovery for PSC as it will provide clues to disease pathogenesis and uncover candidate targets for therapeutic intervention.