Autoimmune Gastritis Complicated by Primary Biliary Cholangitis: A Report of Two Cases and Literature Review

Although autoimmune gastritis (AIG) is often associated with various autoimmune diseases, including type 1 diabetes and Hashimoto's thyroiditis, it is rarely associated with primary biliary cholangitis (PBC). Herein, we present two cases in which AIG was found to be a complication during follow-up of PBC, both histologically diagnosed as AIG with positive autoantibodies and also serologically typical for AIG, including pepsinogen and gastrin. In the first case, a 60-year-old woman with PBC was suspected of having AIG based on endoscopic findings. A definitive diagnosis of AIG was established based on a positive anti-parietal cell antibody test and characteristic histologic findings. The patient exhibited a low pepsinogen I level (5.5 pg/mL; normal: >70 pg/mL) and hypergastrinemia (637 pg/mL; normal: 37-172 pg/mL). Additionally, she was diagnosed with Hashimoto's thyroiditis, confirmed by the presence of anti-thyroid antibodies and an enlarged thyroid gland. In the second case, a 70-year-old woman with PBC was suspected of having AIG due to the low pepsinogen I level (5.8 pg/mL). The definitive diagnosis was established based on the presence of positive anti-intrinsic factor antibodies and characteristic histologic findings. The patient also exhibited hypergastrinemia (2845 pg/mL), but no additional autoimmune diseases were observed. In reviewing past case reports, we identified seven previous reports of AIG with PBC other than our two cases. Approximately half (4/9) were macrocytic anemia, and approximately half (4/9) were positive for anti-thyroid antibodies, which is higher than that expected for conventional PBC. Because AIG should not be misdiagnosed because of the high frequency of associated malignancies, other concomitant autoimmune diseases, and vitamin B12 deficiency, it should be considered in the surveillance of PBC, especially in those with macrocytic anemia or positive antithyroid antibodies.