Adult Nesidioblastosis With Hypoglycemia Mimicking an Insulinoma: A Challenging Case

Introduction: Nesidioblastosis is the primary cause of persistent hyperinsulinemic hypoglycemia in infants but it is a rare entity for the adults. Nesidioblastosis is defined as an increase of pancreatic beta cells in number and in size. Case Presentation: We describe a rare case of nesidioblastosis with positive endoscopic ultrasonography result mimicking an insulinoma. A 35-year-old female patient had hypoglycemic episodes with high insulin level. Her investigation revealed low venous plasma glucose, high insulin and C-peptide level with positive 72-hour fasting test suggestive of hyperinsulinemic hypoglycemia. Abdominal computed tomography did not show any mass lesion. Endoscopic ultrasonography revealed a mass lesion sized as 1 cm in diameter in the pancreas. But, insulinoma like lesion couldn't be found intra-operatively. It was decided to perform distal pancreatectomy. After distal pancreatectomy, nesidioblastosis was diagnosed histopathologically. The patient was free from her symptoms after surgery. Conclusion: This case illustrates difficulties and limitations of imaging modalities and false positive result of EUS in a case of nesidioblastosis. When there is no insulinoma like lesion during operation, operation should be performed as gradient guided pancreatectomy by the way of selective arterial calcium injection test.