Overlap syndrome of seronegative primary biliary cholangitis and small duct primary sclerosing cholangitis: a first case report and literature review.

Primary biliary cholangitis (PBC), primary sclerosing cholangitis (PSC), and autoimmune hepatitis (AIH) are distinct liver diseases. Cases combining PBC and PSC, are extremely rare. Here, we present a case of a 39-year-old woman with a history of colonic Crohn's disease treated with azathioprine. Discontinuation of the medication was prompted by abnormal liver function tests, but subsequent evaluations revealed persistent liver injury. Extensive diagnostic investigations, including imaging, serological tests, and liver biopsy, were conducted leading to a diagnosis of PBC-PSC overlap syndrome based on the presence of concentric lamellar fibrosis and chronic non-suppurative destructive cholangitis. The patient responded well to ursodeoxycholic acid treatment. This case emphasizes the importance of recognizing and diagnosing rare overlap syndromes, particularly those involving PBC and PSC, to ensure appropriate management and improve patient outcomes.