A Case Of Insulin Autoimmune Syndrome: Case Report And Literature Review

Abstract

Background: Insulin Autoimmune Syndrome (IAS) is a rare cause of spontaneous hypoglycemia, characterized by the presence of insulin autoantibodies leading to episodes of hyperinsulinemic hypoglycemia. It is often associated with medication use, particularly sulfhydryl-containing drugs, and is more commonly reported in East Asian populations. The diagnosis of IAS requires a high index of suspicion, particularly in patients with recurrent hypoglycemia and no prior history of diabetes or exogenous insulin use.

Case Presentation: We report the case of a 30-year-old woman admitted with recurrent episodes of fasting and nocturnal hypoglycemia for one month, with glucose levels dropping below 3.8 mmol/L and two documented episodes of neuroglycopenic symptoms, including loss of consciousness. She had no prior history of diabetes but had been taking prednisolone, alpha-lipoic acid, and vitamin B complex without prescription. Laboratory findings revealed significantly elevated fasting insulin (21,525 pmol/L) and C-peptide (3.29 nmol/L) levels, with an insulin-to-C-peptide molar ratio of 6.5. Sulfonylurea screening was negative, and beta-hydroxybutyrate levels were low. Given the suspicion of IAS, insulin autoantibody testing was performed, confirming the diagnosis. The patient was initially managed with dietary modifications and acarbose but continued to experience hypoglycemia. Glucocorticoid therapy with prednisolone 30 mg daily was initiated, leading to glycemic stability. Azathioprine was added for long-term immunosuppression, and prednisolone was gradually tapered.

Conclusion: IAS should be considered in patients presenting with unexplained hypoglycemia and hyperinsulinemia. Early recognition and appropriate management with immunosuppressive therapy and dietary interventions can effectively control symptoms and prevent complications. This case highlights the importance of IAS awareness and contributes to the growing literature on its diagnosis and treatment.