Nesidioblastosis is a rare disease caused by hyperplasia of pancreatic islets, developing a state of hypoglycemia due to an increase in the insulin production. It is the leading cause of hyperinsulinic hypoglycemia in childhood, whereas in adults it only represents the 0.5-5% of cases. The pathogenesis is still unknown. We have studied several genetic mutations associated with dependent potassium channel of ATP present in the beta cells of the pancreas, as well as in patients underwent bariatric surgery because of the metabolic changes involved. Woman (38 years old) attends consultation of General Surgery derived from Endocrinology before symptoms of persistent hypoglycemia. Factitious hypoglycemia and syndromes of neuroendocrine origin were ruled out. Imaging tests failed to identify space-occupying lesions. The medical treatment failed, persisting hypoglycemia symptoms. Before the given analytical and radiological findings obtained, and the persistence of symptoms affecting the quality of life of the patient, we opted for surgical treatment performing a pancreatectomy of the 80% of the gland. The final pathologic diagnosis was nesidioblastosis. Nesidioblastosis is a rare pathology, but it must be present in the differential diagnosis of hypoglycemia symptoms with endogenous hyperinsulinism in adults, once the intake of sulfonylureas and possible pancreatic neoformations have been ruled out. Copyright © 2013 IAP and EPC. Published by Elsevier B.V. All rights reserved.