Insulinoma: unusual presentation

Abstract

The authors describe a rare and unusual presentation of insulinoma in a 12-year-old girl. The child was being followed up by the paediatric team for constitutional short stature and eating and behavioural disorders, and developmental delay. She presented at 12 years of age with a history of frontal headache followed by a generalised tonic–clonic seizure. Her bedside glucostix showed a blood glucose of 2.3. She had further episodes of symptomatic hypoglycaemia, needing glucagon administration and IV 10% dextrose administration. Her blood tests showed a true lab glucose of 2.2, an inappropriately high insulin level of 70 pmol/l, C peptide 617 pmol/l, growth hormone 1.23 mcg/l. Insulin-like growth factor-1, insulin-like growth factor-binding protein, lactate, ammonia and cortisol levels were within normal limits. Urinary ketones were absent during the hypoglycaemic episode. MRI abdomen showed a 1-cm lesion in the uncinate process of the pancreas, hyperintense on T2 weighed images and demonstrates heterogeneous enhancement. The lesion was just anterior to the common bile duct, at the level of the right renal hilum. The MRI changes were suggestive of Insulinoma. She was started on octreotide, awaiting surgery. It was difficult to control her hypoglycaemia, especially at night time. Therefore, she required prolonged inpatient admission and intravenous fluid therapy. Octreotide was switched to diazoxide as she remained hypoglycaemic. She had a resection of the Insulinoma and pancreatic jejunostomy done successfully. Repeat testing after the operation showed an insufficient growth hormone response. Testing for MEN 1 gene was negative. She remains well on her current treatment. Insulinoma is a rare neuroendocrine tumour, with an incidence of 3–10 cases per million per year. It is the commonest cause of hypoglycaemia from endogenous hyperinsulinism. About 90% are benign. It is not uncommon to initially mistake the symptoms of hypoglycaemia for behavioural disorders. As most of them are benign, they have a good cure rate with complete resection.