Insulin Autoimmune Syndrome - A Case Series

An Unusual Case of Hypoglycemia in a Non-diabetic Individual due to Hirata Disease

Hypoglycemia is common in diabetic populations using insulin or insulin secretagogues, but rare in non-diabetics. A 60-year-old non-diabetic male presented with repeated episodes of abnormal behavior persisting for 10-15 minutes for seven days, associated with sweating, intense hunger, and relief on food intake, with no history of insulin or secretagogue intake, with stable vitals and normal systemic examination. Laboratory tests during attacks revealed low blood sugar, high serum insulin, and normal C-peptide levels, with no evidence of pancreatic or extrapancreatic hyperinsulinism, and serum anti-insulin antibody levels >100 U/ml. Based on these results, he was diagnosed with autoimmune insulin syndrome (AIS). Treatment with low-carb meals, oral prednisolone, and acarbose led to the resolution of symptoms. Hirata syndrome, though rare in India, requires consideration as a differential diagnosis to avoid unnecessary invasive procedures.

A Case of Insulin Autoimmune Syndrome in an Indian Male Taking Alpha-Lipoic Acid

Insulin autoimmune syndrome [IAS, Hirata disease (HD)] is a rare cause of recurrent spontaneous hypoglycemic episodes, characterized by high serum insulin levels and high titers of autoantibodies against endogenous insulin. We report a case of a previously healthy Indian male presenting with recurrent episodes of hypoglycemia with no prior exposure to exogenous insulin. Regular glucose monitoring was done. Laboratory tests showed insulin >1000 μIU/mL and C-peptide levels of 12.8 ng/ml. The patient had high titers of insulin autoantibodies (IAA) (>100 units/mL; normal range: <10 units/mL), which indicated a diagnosis of IAS. The patient was consuming alpha-lipoic acid; sulfhydryl-containing compounds have been linked to IAS. This case report highlights the importance of IAA titers in first-line investigations for hypoglycemia in a non-diabetic patient with strikingly high blood insulin levels and discusses the potential relationship between IAS and alpha-lipoic acid.

Exogenous Insulin Antibody Syndrome in Patients with Type 2 Diabetes

Background

Exogenous insulin antibody syndrome (EIAS) is an immunological disorder caused by circulating insulin antibodies (IAs), featuring hypersensitivity to exogenous insulin and insulin resistance. With the wide use of recombinant human insulin and insulin analogs, there has been a significant proliferation of EIAS.

Case Report

We describe two cases of diabetes mellitus (DM) with hyperinsulinemia and high serum levels of IAs. They had never been exposed to methimazole, glutathione, lipoic acid, and other sulfhydryl drugs, but they all received insulin treatment. The patient in case 1 had recurrent hypoglycemia before hospitalization. A prolonged oral glucose tolerance test (OGTT) showed hypoglycemia with inappropriately high insulin levels. The patient in case 2 was hospitalized for diabetic ketosis. An OGTT indicated hyperglycemia with hyperinsulinemia and low levels of C-peptide. IAs induced by exogenous insulin in the two patients with DM were positive at high titers, prompting a diagnosis of another condition-EIAS.

Conclusion

We discussed the differences between these two cases of EIAS in clinical manifestations and treatment and summarized all patients of EIAS treated in our department to date.

An Uncommon Case of Recurrent Hypoglycemic Episodes in a Healthy Non-diabetic Male: Insulin Autoimmune Syndrome

Insulin autoimmune syndrome is a rare cause of recurrent hypoglycemic episodes that can mimic various other pathological problems leading to unnecessary diagnostic assessments and interventions. Here, we report a case of a healthy non-diabetic male in his 50s presenting with recurrent episodes of hypoglycemia with no prior exposure to exogenous insulin. During a 72-hour fasting test, his glucose levels reached 22 mg/dl within less than three hours. The lab tests showed insulin of 1000 μIU/mL and C-peptide of 4.99 ng/ml. On further evaluation, high titers of insulin autoantibodies (IAA) >100 U/ml (normal = <10 U/ml) were consistent with insulin autoimmune syndrome diagnosis. This case thus highlights the importance of including IAA titers in first-line investigations for hypoglycemia in a non-diabetic patient with strikingly high blood insulin levels.

Insulin Autoimmune Syndrome: A Systematic Review

Insulin autoimmune syndrome (IAS) is a rare endocrine disorder characterized by recurrent episodes of severe hypoglycemia, markedly elevated serum insulin, and positive insulin autoantibodies. In recent years, various countries have reported it one after another. It can be seen that we must pay attention to this disease. The diagnosis of IAS is challenging, requiring a careful workup aimed at excluding other causes of hyperinsulinemic hypoglycemia. High levels of insulin autoantibodies are found in patients, and C-peptide is not parallel to insulin, which could be diagnostic. IAS is a self-limiting disease with a good prognosis. Its treatment mainly includes symptomatic supportive treatment, such as adjusting the diet and using acarbose and other drugs to delay the absorption of glucose to prevent hypoglycemia. For patients with severe symptoms, available treatments may include drugs that reduce pancreatic insulin secretion (such as somatostatin and diazoxide), immunosuppressants (glucocorticoids, zaprin, and rituximab), and even plasma exchange to remove autoantibodies from the body. This review provides a comprehensive analysis of the epidemiology, pathogenesis, clinical manifestations, diagnosis and identification, and monitoring and treatment management of IAS.

Alternative cause for hypoglycaemia in insulin-treated diabetes mellitus

We present a case of a 73-year-old woman who developed recurrent hypoglycaemia during a prolonged hospital stay following a mechanical fall. She had a complex history of insulin-treated diabetes mellitus, hypothyroidism, diffuse systemic cutaneous sclerosis, Raynaud's disease, previous breast cancer, Barrett's oesophagus and previous partial gastrectomy for a benign mass. Hypoglycaemia persisted despite weaning of insulin. She had no clinical features of adrenal or pituitary insufficiency with an acceptable cortisol on stopping prednisolone and had an optimal thyroid replacement. A 72-hour fast elicited hypoglycaemia with corresponding low insulin level. Although the C-peptide was detectable, there were no clinical, biochemical or radiological features suggestive of insulinoma. Reactive hypoglycaemia post partial gastrectomy was ruled out based on limited relation of the hypoglycaemia to meals and the low insulin levels. Hydroxychloroquine (HCQ)-induced hypoglycaemia was considered based on previous case reports and the recent literature, with a successful resolution of hypoglycaemia on discontinuation of HCQ.