The significant IgG4 infiltrate in autoimmune hepatitis is associated with a greater ductular reaction and more advanced liver disease.

Background: Sclerosing cholangitis is the typical IgG4-related disease digestive involvement. However, the role of the IgG4 liver expression in autoimmune hepatitis remains unknown.

Aims: to assess whether the expression of IgG4 plasma cells in patients with autoimmune hepatitis (AIH) was associated with different outcomes.

Methods: Retrospective study including patients diagnosed with AIH by biopsy from January-2009 to June-2021. At least mild IgG4 expression (>10 IgG4-plasma cells per field) was considered as significant.

Results: 85 patients with AIH were included. Overall, 58.8% were women, mean age 54 years. Nine (10.6%) presented cirrhosis at diagnosis. Fifteen (17.6%) had significant IgG4 liver expression. Patients with IgG4 infiltrate were older (p = 0.021), presented liver cirrhosis more frequently (33.3% vs. 5.7%, p = 0.007), greater IgG plasma values (p = 0.008) and atypical ANCAs (p = 0.086); ductular reaction was also more common (p = 0.009). Complete remission rate was similar regardless of the IgG4 infiltrate. Time to corticosteroids discontinuation was longer in subjects with IgG4 infiltrate (p = 0.068), but second-line therapy tended to be less frequent (p = 0.187).

Conclusion: Significant IgG4 liver infiltrate in patients with autoimmune hepatitis is associated with more advanced liver disease. The greater ductular reaction mediated by the IgG4 infiltrate may be the cause for this finding, though this finding should be prospectively assessed.