A Novel Pathogenic MEN1 Gene Variant Identified in a Family With Multiple Pancreatic Neuroendocrine Tumors

Multiple endocrine neoplasia type 1 (MEN1) is a hereditary endocrine tumor syndrome caused by pathogenic variants in the MEN1 gene, and most patients with this syndrome initially develop primary hyperparathyroidism (PHPT). Here, we report the case of a family wherein a germline MEN1 variant was detected and multiple pancreatic neuroendocrine tumors (PanNETs) were observed at the initial evaluation. A 40-year-old woman presented with a complaint of abdominal discomfort, and a close examination revealed multiple pancreatic tumors. Distal pancreatectomy with splenectomy was performed, and the diagnosis was nonfunctional PanNETs. Five years later, her 76-year-old mother was referred to the hospital with multiple pancreatic tumors. A genetic test revealed that both patients harbored a previously unreported germline variant in the MEN1 gene. Although it was classified as a variant of uncertain significance, we suspect that it may be associated with the pathogenesis of these lesions. This case report presents a new disease concept—familial isolated pancreatic neuroendocrine tumors, or FIPNETs—in patients harboring a pathogenic variant in the MEN1 gene who experience only pancreatic lesions. We suggest that clinicians consider genetic testing for the MEN1 gene in patients with multiple pancreatic lesions who show no signs of PHPT.