LAUSR

BACKGROUND Immunoglobulin G4-related disease (IgG4-RD) is a multi-system fibroin-flammatory disorder that can involve any organ, including the salivary glands, pancreas, and biliary tree. Treatment of immunoglobulin G4-related sclerosing cholangitis (IgG4-SC) is similar to that for IgG4-RD, but progression is irreversible in some cases. We present a case of IgG4-SC in which an immuno-suppressant induced marked clinical and radiologic improvement. CASE SUMMARY A 63-year-old male presented with a prominent itching sensation and wholebody jaundice. He showed obstructive-pattern jaundice, an elevated IgG4 level, and infiltration of a large number of IgG4-positive cells in the ampulla of Vater. The imaging findings of intrahepatic duct (IHD) and common bile duct dilation, an elevated serum IgG4 level, and characteristic histological findings led to diagnosis of IgG4-SC that compatible with the 2019 ACR/EULAR classification criteria. We planned to treat the patient with high-dose glucocorticoid (GC), followed by cyclophosphamide pulse therapy. After treatment with high-dose GC and an immunosuppressant, imaging studies showed that IHD dilatation had completely resolved. CONCLUSION Prompt diagnosis and appropriate treatment of IgG4-SC are important. Because there is a risk of relapse of IgG4-SC, the GC dose should be gradually reduced, and a maintenance immunosuppressant should be given.