This patient had ERCP and biopsy of the CBD stricture with no malignant cells identified. Immunological serology demonstrated elevated IgG4. 

The main differential to exclude in a patient of this age is cholangiocarcinoma. The associated diffusion restriction of the pancreas and elevated IgG4 with a negative biopsy makes the diagnosis of autoimmune pancreatitis with associated IgG4-related sclerosing cholangitis the favored differential. These entities are associated 90% of the time.

The patient's age and absence of inflammatory bowel disease make primary sclerosing cholangitis less likely, which although also autoimmune related, is a separate entity.