Fibrous dysplasia of bone /McCune Albright syndrome (FD/MAS) is a rare bone disease caused by somatic mutations in GNAS gene. This GNAS mutation predisposes to cancers, including breast cancer, thyroid cancer, chondrosarcoma and osteosarcoma, as well as biliary tract anomalies, liver-tumors or pancreatic tumors - IPMNs. Intraductal papillary and mucinous neoplasms of the pancreas (IPMN) are cystic intraepithelial ductal lesions developed at the expense of pancreatic ducts. They are pre-cancerous lesions, requiring monitoring and, in case of progression or malignant degeneration, surgical resection. Pancreatic MRI screening of patients with polyostotic FD and MAS is recommended. The aim of this study is to investigate the epidemiology and characteristics of these hepato-pancreato-biliary abnormalities (prevalence, age of onset, degeneration), based on magnetic resonance imaging (MRI) realized during the follow-up of patients with FD/MAS treated in a French FD expert center. A better understanding of these IPMNs and other digestive abnormalities will enable clinicians to improve the management and monitoring in this high-risk population.