Abstract: In this paper, we report an elderly patient who had been experiencing poor appetite for one month and yellowing of the skin and sclera for two months before visiting the Department of Geriatrics at Peking Union Medical College Hospital. The patient's blood tests revealed significantly elevated levels of serum total bilirubin, direct bilirubin, and blood sugar. The serum IgG4 level nearly tripled. Abdominal imaging examinations revealed diffuse pancreatic lesions, narrowing of the intrapancreatic segment of the common bile duct, and thickening and marked enhancement of the common hepatic duct, left and right hepatic ducts, and branches. Blood glucose was also significantly elevated during the course of the disease. Moreover, nutritional assessment found that the patient was malnourished. After multidisciplinary discussion, a medium dose of oral methylprednisolone was prescribed to the patient due to his advanced age and multiple chronic conditions. The dose was then quickly reduced while the patient simultaneously received low-dose mycophenolate mofetil (MMF) treatment. As a result, the patient's bilirubin level significantly decreased, jaundice subsided, and his body weight returned to normal with improved physical function. Throughout the diagnosis and treatment process, a multidisciplinary team actively participated in discussions and gradually identified the underlying cause. This exemplifies the crucial role of interdisciplinary collaboration in effectively diagnosing and treating complex illnesses in elderly patients.