Hypoglycemia due to Insulin Autoimmune Syndrome: A rare cause not to be forgotten

Most cases of recurrent hypoglycemia occur in patients with diabetes mellitus and can be prevented by changes in medications, diet or activity. However, a person with unexplained hypoglycemia can indicate potentially grave, often treatable underlying disorders such as insulinoma, Addison's disease or hypopituitarism. Medication is another cause of unexplained hypoglycemia. A focused laboratory work-up is essential, often a plasma/serum glucose, insulin and C-peptide. Normal or high insulin and C-peptide levels indicate excessive endogenous insulin production. We are reporting a case of Insulin Autoimmune Syndrome (IAS) in a 38-year-old Indian female who presented to us with recurrent episodes of spontaneous hypoglycemia. On evaluation, the patient was found to have Endogenous Hyperinsulinemic Hypoglycemia (EHH). As no obvious cause of EHH was found on abdominal imaging, we further evaluated her for insulin antibodies which were found to be raised. A diagnosis of IAS was made and the patient was put on a diet of frequent small meals and she improved. Most cases of this syndrome have been reported from Japan and very few case reports of IAS exist in India. Thus IAS, though rare, should be kept in the differential diagnosis of spontaneous hypoglycemia. Keywords: Hypoglycemia, Insulin antibodie