[Autoimmune pancreatitis and IgG4-related hepatic inflammatory pseudotumor complicated by an impacted pancreatic stone at the major papilla during steroid treatment].

A 79-year-old male presented to our hospital with abdominal discomfort and was diagnosed with mass-forming pancreatitis. During follow-up, pancreatic stones and a hepatic mass with peripheral bile duct dilation were discovered. Serum IgG4 level was elevated, and a liver tumor biopsy revealed numerous IgG4-positive plasma cells and fibrosis. Chronic pancreatitis with the suspected involvement of autoimmune pancreatitis (AIP) and IgG4-related hepatic inflammatory pseudotumor (IgG4-HIP) was diagnosed. Therefore, a steroid treatment was initiated. However, 2 months later, the patient complained of epigastric pain that was found to be caused by an impacted pancreatic stone in the major papilla, which was endoscopically removed. Follow-up imaging findings confirmed the improvement in AIP and the dissolution of the IgG4-HIP.