Abstract BACKGROUND: Among the causes of hyperinsulinemic hypoglycemia in adults, nesidioblastosis accounts for 7%. CLINICAL CASE: A 43-year-old female patient with a history of diabetes mellitus and primary arterial hypertension that began with hypoglycaemia that persisted for 5 months; insulin was suspended. Patient was hospitalized due to generalized tonic-clonic seizure and hypoglycaemia of 10 mg/dL, fasting test was performed with hypoglycemia at 8 h of 65 mg/dL, insulin 14.2 µUI/mL and peptide C 2.52 ng/mL; she was referred at the third level hospital, where nuclear magnetic resonance and selective intra-arterial pancreatic stimulation were performed with inconclusive results. In the medical surgical session it was decided to perform distal pancretectomy. Histopathological report was of islet cell hyperplasia of Langerhans, immunohistochemistry: chromogranin A +, synaptophysin +, neuronal enolase +, CD 56 + and Ki67 < 1%. CONCLUSIONS: Nesidioblastosis in adults is a rare disease with an increased incidence. KEYWORDS: Nesidioblastosis; Hyperinsulinism; Pancreatectomy.