Abstract: Objective To analyze the histopathological changes of autoimmune hepatitis (AIH)-primary biliary cholangitis (PBC) overlap syndrome and to improve the understanding of its clinical and pathological features.Methods The pathological changes of liver tissue in 10 patients with AIH-PBC overlap syndrome were retrospectively analyzed. Results The AIH-PBC overlap syndrome was more common in middle-aged women (80%) presenting with clinical and pathological characteristics of both AIH and PBC. Interface hepatitis, bridging necrosis and central confluence necrosis were all observed. The inflammatory activity of the liver tissue was from moderate to severe and fibrosis score was from S2 to S4. At the same time, different degrees of small bile duct lesions were observed, including 3 cases with obvious bile ducts decrease and 2 cases with small bile duct hyperplasia.Conclusion Diagnosis of AIH-PBC overlap syndrome should be based on the clinical presentation and changes in biochemistry, immunology and histology. The overlap syndrome has the histopathological features of both AIH and PBC, with main histological changes of interface hepatitis, bridging necrosis and small bile duct reduction.

Key words: Autoimmune hepatitis, Primary biliary cholangitis, Overlap syndrome, Pathology