Clinicopathological Features of Autoimmune Hepatitis with IgG4-Positive Plasma Cell Infiltration.

Background: We aimed to elucidate the characteristics and prognosis of autoimmune hepatitis (AIH) patients with immunoglobulin (Ig) G4-positive plasma cell infiltration.

Methods: We enrolled 84 AIH patients. The number of IgG- and IgG4-positive plasma cells was immunohistochemically counted per high-power field in the portal area. Patients with 3 or more IgG4-positive plasma cells on average and a ratio of IgG4 to IgG-positive plasma cells ≥5% were defined as IgG4-associated AIH (IgG4-AIH), and their clinicopathological characteristics and prognosis were compared to those of the remaining classical-AIH patients.

Results: Ten (11.9%) and 74 patients (88.1%) were categorized as IgG4-AIH and classical-AIH patients, respectively. The median age of the IgG4-AIH patients was 67 years, the majority was female (80.0%), and the distribution was similar to that of the classical-AIH patients. The IgG4-AIH patients exhibited significantly more severe phenotypes in portal inflammation, interface hepatitis, fibrosis, and rosette formation. All clinical laboratory data were similar except for serum IgG4 levels, which were higher in IgG4-AIH patients (168.5 vs. 22.9 mg/dL, p = 0.014). During a median follow-up period of 139 months, the relapse rate was significantly lower in the IgG4-AIH group than in the classical-AIH group (11.1 vs. 49.2%; p = 0.048). Twelve (16.2%) and 6 (8.1%) classical-AIH patients underwent liver-related events and liver-related deaths, respectively. In contrast, none of the IgG4-AIH patients progressed to severe liver disease.

Conclusions: The IgG4-AIH patients had more severe inflammation and advanced fibrosis in the liver. However, their prognosis was not poor compared to that of classical-AIH patients. IgG4-AIH may have a phenotype distinct from classical-AIH.