IgG4-AIH with multiple inflammatory pseudotumors and decreased OATP1B3 expression.

Autoimmune hepatitis (AIH) is a chronic inflammatory liver disease caused by an autoimmune response to hepatocytes, predominantly affecting middle-aged and older women. A subset of AIH cases has been associated with immunoglobulin G4-related disease (IgG4-RD), referred to as IgG4-AIH. This rare condition is characterized by IgG4-positive plasma cell infiltration in the portal area and elevated serum IgG4 levels. Despite its rarity, IgG4-AIH has been proposed as a distinct disease entity. Here, we report a case of IgG4-AIH associated with multiple inflammatory pseudotumors (IPTs) and decreased organic anion transporting peptide (OATP) 1B3 expression. Hepatic IPTs are typically composed of lymphoplasmacytic and fibroblastic accumulations. In the present case, OATP1B3 expression was relatively decreased without such accumulation according to IgG4-related inflammation, suggesting that IgG4-related inflammation may regulate OATP1B3 expression.