Case Report: A Case of Adult Nesidioblastosis

Abstract

Background: Adult nesidioblastosis is an extremely rare cause of hyperinsulinaemic hypoglycaemia, however its diagnosis has been on the rise in recent years. It is characterised by beta-cell hypertrophy and diffused islet hyperplasia. In contrast to infantile nesidioblastosis secondary to a genetic defect, the cause of adult nesidioblastosis is largely unknown. Case report: We report a case of hyperinsulinaemic hypoglycaemia in an 83-year-old man with biochemical derangements consistent with a diagnosis of insulinoma. Preoperative cross-sectional imagings, Dotatate PET, and visceral angiogram all failed to definitively localise a neuroendocrine tumour. Selective arterial calcium stimulation showed a subtle increase in insulin secretion from the tail of the pancreas. After an unrevealing intraoperative ultrasound, a distal pancreatectomy was performed with pathology showing diffused islet hyperplasia consistent with a diagnosis of nesidioblastosis. Postoperative euglycaemia was achieved and persisted to the time of manuscript submission four months later. Conclusion: Clinically and biochemically it is extremely difficult to distinguish nesidioblastosis from insulinoma. The sensitivity of different preoperative localising modalities for insulinoma varies with the gold standard being selective arterial calcium stimulation. In contrast to insulinoma, response to selective arterial calcium stimulation could be subtle in nesidioblastosis, and such subtlety should raise the suspicion for the latter especially in the presence of unrevealing imaging findings. Given reports of coexistence of insulinoma and nesidioblastosis along with other known entities such as multifocal insulinoma and focal nesidioblastoma, we postulate pathological beta cell hyperplasias fall on a continuous spectrum of hyperfunctioning beta cell disorders as opposed to the current dichotomous understanding.