Association of malignant insulinoma and type 2 diabetes mellitus: a case report

We report a case of recurrent hypoglycemia due to malignant insulinoma in a type 2 diabetic patient correctly controlled for years with the same doses of oral antidiabetic agents. A 79-year-old woman was admitted for recurrent severe hypoglycemia. She had a history of type 2 diabetes since 2000. HbA1c was 7.8% when she reported mild hypoglycemia and 5.8% when recurrent hypoglycemia appeared despite progressive diminution of glicazide. Severe hypoglycemia continued despite interrupting diabetes medications. At admission, results showed inappropriately elevated insulin, C-peptide and proinsulin levels despite significant hypoglycemia. CT scan showed "cystic" nodes in the pancreas and in the liver. Liver biopsy found a well-differentiated neuroendocrine carcinoma with positive staining for chromogranin A and negative staining for insulin. Hypoglycemia improved with diazoxide, lanreotide and dextrose infusion. Liver chemoembolization was planned. Severe edema, dyspnea, hyponatremia, and hypo-osmolarity occurred. The patient's clinical status deteriorated rapidly with severe cardiac, renal and hepatic failure. She died in a few days. Association of diabetes mellitus and insulinoma is extremely rare. Malignant insulinoma survival is less than two years, shorter when hepatic localizations are present at diagnosis. Association of diabetes with insulinoma delays the diagnosis, but does not alter prognosis or favor carcinoma frequency. Lanreotide was inefficient in our patient despite good responses described in the literature. Heart, respiratory and renal failures have been described with diazoxide independently of the doses; this may in part explain the rapid death. Insulinoma should be considered as a cause of unusual and recurrent hypoglycemia in a diabetic patient especially if it persists after interrupting antidiabetic agents.