Clinical and pathological features of autoimmune hepatitis-primary biliary cholangitis overlap syndrome versus autoimmune hepatitis

Objective To investigate the clinical and pathological features of autoimmune hepatitis (AIH) -primary biliary cholangitis (PBC) overlap syndrome (AIH-PBC OS) versus AIH, since it is still difficult to diagnose AIH-PBC OS in clinical practice, and to enhance the knowledge of AIH-PBC OS and improve its early diagnostic rate.Methods A prospective study was performed for the clinical data, biochemical and immunological markers, autoantibody, and liver pathology of 50 patients with AIH-PBC OS confirmed by liver biopsy who visited West China Hospital, Sichuan University, from January 20, 2015 to November 28, 2016 and 57 patients with AIH alone, in order to compare the features of AIH-PBC OS and AIH.Continuous data such as laboratory markers were expressed as median M (inter-quartile range) and the nonparametric rank sum test was used for comparison of these data between two groups;categorical data including clinical features、histopathological manifestations were expressed as rates and the chi-square test was used for comparison of these data between two groups.Results The AIH-PBC OS group had a significantly lower age of onset than the AIH group (Z=-1.975, P=0.048) , while there was no significant difference in male/female sex ratio between the two groups.The AIH-PBC OS group had a significantly higher proportion of patients with pruritus than the AIH group (22.0% vs 7.0%, χ2=4.960, P=0.026) .Compared with the AIH group, the AIH-PBC OS group had significantly higher levels of alkaline phosphatase (ALP) , gamma-glutamyl transpeptidase (GGT) , and immunoglobulin M (IgM) (Z=-6.250, -4.789, and-5.407, all P<0.001) , a significantly higher positive rate of antimitochondrial antibody (AMA) (χ2=26.811, P<0.001) , and significantly lower serum levels of alanine aminotransferase (ALT) , aspartate aminotransferase, and immunoglobulin G (IgG) (Z=-2.916, -3.381, and-2.285, P=0.004, 0.001, and 0.022) .The AIH-PBC OS group had significantly higher incidence rates of bile duct injury, bile duct loss, granulomatous disease, and cholestasis than the AIH group (χ2=25.612, 15.953, 6.490, and 10.042, P<0.001, <0.001, 0.001, and 0.002) .Conclusion Although AIH-PBC OS has the features of both AIH and PBC, it is not a simple overlap between AIH and PBC.Pruritus, significant increases in the levels of ALP, GGT, and IgM, positive AMA, and inflammatory bile duct disease and cholestasis may have implications for the diagnos of AIH-PBC OS.Since AIH-PBC OS may have milder liver inflammatory injury and autoimmune abnormalities than AIH, the levels of ALT and IgG in Paris criteria can be broadened during the diagnosis of AIH-PBC OS, in order to prevent missed diagnosis and avoid affecting the selection of treatment regimen and patients' prognosis.