IgG4-Related Sclerosing Cholangitis Mimicking Cholangiocarcinoma.

IgG4-related sclerosing cholangitis (IgG4-SC) is a relatively newly identified disease that is frequently associated with autoimmune pancreatitis. The differential diagnosis between cholangiocarcinoma, primary sclerosing cholangitis, and IgG4-SC can be challenging due to significant overlap among the clinical and imaging characteristics. We report the case of a 71-year-old woman who was diagnosed with IgG4-related disease based on increased serum IgG4 levels, imaging, and clinical presentation, which showed systemic involvement, including sclerosing cholangitis and kidneys. The patient presented with chronic jaundice. Magnetic resonance imaging revealed bile duct strictures and the dilatation of upstream bile ducts, smooth wall thickening with uniform enhancement in the delayed phase, and no vascular infiltration. Multiple low-density, wedge-shaped areas were identified in both kidneys, which were hypointense on T2-weighted images and hyperintense on diffusion-weighted images. The serum IgG4 levels of this patient were elevated to nearly 10-fold the normal upper limit. A diagnosis of IgG4-SC associated with IgG4-related kidney was made. Based on this case, pre-surgery IgG4 serum treatment in patients with non-malignant bile duct stenosis was recommended to exclude IgG4-SC.