MON-135 A Case of Hirata’s Disease

Abstract

Introduction- Insulin Autoimmune Syndrome (IAS), also known as Hirata's disease, is a rare cause of endogenous hyperinsulinemic hypoglycemia, characterized by episodes of spontaneous hypoglycemia with high serum insulin and elevated insulin autoantibodies in the individuals who have not received exogenous insulin. Only few cases have been reported in Caucasians while there have been more than 300 cases from Japan. Given the rarity of this condition outside of Japan, here we report a case of Hirata’s disease. Case Presentation- A 59-year-old male was brought in to the emergency room with altered mental status and slurred speech. Patient's initial blood glucose was 30 and was given dextrose 10 (D10) en route with remarkable improvement in his mental status and speech and resolution of neuroglycopenic symptoms. Patient’s vital signs and physical exam was unremarkable. Basic initial laboratory workup was unremarkable. He reported no similar episodes in the past. He is not any medications known to cause hypoglycemia. ACTH, cortisol, TSH and T4 levels were normal. Sulfonylurea screen was negative. Hospital Course was complicated by recurrent, symptomatic hypoglycemic events with blood glucose as low as 37mg/dL. Initial suspected diagnosis was insulinoma and he was started on octreotide and D10 drip with continued hypoglycemia episodes postprandial. For further work up, insulin, c-peptide, proinsulin, insulin antibody were ordered during hypoglycemia episode. C-peptide was 3.7 (ULN 3.5) and insulin 156 (ULN 19) and insulin antibody > 50 (ULN 0.4). MRI abdomen revealed normal appearing pancreas and adrenal glands. Based on the presence of high titers of insulin antibodies and high insulin and relatively normal c-peptide levels accompanied by recurrent postprandial hypoglycemia’s, diagnosis of IAS was suspected and was then started on prednisone with a marked decrease in frequency of hypoglycemic episodes. Patient was discharged on oral prednisone with follow up with endocrinologist and is doing well on last outpatient follow up. Discussion- Mechanism of IAS is not well understood and is assumed to be due to antibodies against insulin that initially bind and later releases insulin asynchronously. Eighty percent of IAS patients spontaneously remit. In some individuals, IAS is associated with medications that contain ‘sulfhydryl’ group rendering insulin more immunogenic. Corticosteroids, plasmapheresis and immunosuppressants have been used to treat IAS. A diet consisting of several light meals per day, avoiding simple sugars, is recommended. Conclusion- IAS is a rare cause of hypoglycemia, and it should be suspected in non-diabetic patients with spontaneous hypoglycemia in whom there is failure to localize an abdominal tumor and who demonstrate extremely high insulin levels. Insulin autoantibodies should be tested in such patients to avoid unnecessary invasive testing and surgery.