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Background
Insulin autoimmune syndrome (IAS, Hirata disease) is characterised by a combination of fasting or postprandial hypoglycaemia, high serum insulin levels and presence of insulin autoantibodies in the absence of exogenous insulin administration. 1 Hypoglycaemia, in the absence of a glycaemic-lowering agent, can present as a diagnostic challenge. Failure to recognise the underlying cause of spontaneous hypoglycaemia can have potentially fatal consequences. We report a case of IAS in South Asia-where the condition has been virtually unreported-induced by a commonly used antithyroid drug.
Case presentation
A 23-year-old Nepali man was brought to the emergency department (ER) in an unconscious state. He had no history of fever, headache, vomiting, weight loss or seizure-like activity. His Glasgow Coma Scale (GCS) score was 6 (E2V1M3) at the time of presentation. He was of normal weight (body mass index 23.13 kg/m2 ) and his vitals were stable (blood pressure 130/70 mm Hg, pulse rate 72/min). Physical examination revealed a diffusely enlarged, non-tender thyroid. The rest of the examination revealed no abnormalities. Two years ago, the patient had been diagnosed as having Graves' disease, and was on carbimazole 30 mg/day. After a lapse in medication for around 3 months, the patient had restarted his treatment 6 weeks back. He had no history of diabetes mellitus, no other concurrent illnesses and no exposure to insulin or antidiabetic agents. He was on a normal diet. There was no family history of diabetes mellitus. On investigation, his random blood glucose was 19 mg/dL. All other routine laboratory tests were within normal limits. The patient regained consciousness after hypoglycaemia was corrected with intravenous dextrose infusion. He was sent home and advised to follow-up for evaluation in the medical outpatient department. Four days later, the patient was found unconscious on his bed and brought to the ER again. History and examination did not reveal any findings at variance with those of the previous episode. The patient had persistent hypoglycaemia despite intravenous dextrose infusion, and was admitted to the hospital for further evaluation.
Investigations
During the second ER visit, the patient's initial random blood glucose was 44 mg/dL. Repeat random blood glucose after dextrose infusion was 10 mg/dL. During the hospital stay, six hourly random blood glucose revealed recurrent episodes of hypoglycaemia (ranging from 37...