Primary sclerosing cholangitis (PSC) is a rare chronic inflammatory disease of the bile ducts and is difficult to treat, since its causes have not yet been adequately researched. Using RNA sequencing, an international research consortium led by Michael Trauner, Head of MedUni Vienna’s Division of Gastroenterology and Hepatology (Department of Medicine III), has now identified a new prognostic factor for PSC from liver biopsies. This is so-called cellular ER stress. ER stress is the name given to a complex cellular response to stress caused by the build-up of misfolded proteins in the endoplasmic reticulum (ER).