Case history: A 42 year old female presented with a history of collapse and seizure activity. Her blood glucose was noted to be 3.1 with the paramedics and subsequent hypoglycaemia was demonstrated on several occasions whilst in hospital. She described a family history of insulinoma in her mother. A 72 h fast was performed as an inpatient to look for insulinoma. The nadir serum glucose was 2.0 mmol/l with an inappropriate C-peptide level of 1006 pmol/l and an insulin level of 12 μ/l.
A CT and MRI of the pancreas showed no evidence of pancreatic or hepatic abnormalities. We proceeded to endoscopic ultrasound, which demonstrated a 14 mm lesion in the portal confluence of the pancreas. Calcium stimulation insulin venous sampling was strongly suggestive for hyperinsulinaemia in the superior mesenteric artery. She was commenced on diazoxide and later had a subtotal pancreatectomy. Histology delineated a grade one T1N0 neuroendocrine tumour, with Ki-67 of 45%. The patients mother had had surgical resection for a histology ally proven insulinoma. As such, genetic testing was performed on this patient to exclude multiple endocrine neoplasia, which was negative for the MENIN gene.
Discussion: Familial insulinoma is very rare in the absence of MEN, however it does need to be considered. This has implications for family screening.