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Case Reports
. 2024 Jul 9;16(7):e64130.
doi: 10.7759/cureus.64130. eCollection 2024 Jul.

Insulin Autoimmune Syndrome: A Case Report Highlighting Diagnostic Pitfalls

Hisatoshi Okumura  1 , Satoshi Inaba  2 , Atsushi Kawashima  2 , Taro Shimizu  3
Affiliations
Case Reports

Insulin Autoimmune Syndrome: A Case Report Highlighting Diagnostic Pitfalls

Hisatoshi Okumura et al. Cureus. .

Abstract

Insulin autoimmune syndrome (IAS) is characterized by spontaneous hyperinsulinemic hypoglycemia and the presence of insulin autoantibodies in high titers without exogenous insulin use. The C-peptide level during a hypoglycemia episode is useful for differentiating spontaneous hypoglycemia. Generally, low C-peptides are suspicious for exogenous insulin administration. We report a 47-year-old male nurse who presented with an initial episode of hypoglycemia. Despite the pattern of hyperinsulinemic hypoglycemia and low C-peptide, he was diagnosed with IAS based on the presence of insulin autoantibodies. This case underscores the importance of suspecting IAS in non-diabetic adults with hypoglycemia, even in the setting of low C-peptide levels.

Keywords: exogenous hyperinsulinemia; hyperinsulinemic hypoglycemia; insulin autoimmune syndrome; non-diabetic adults; spontaneous hypoglycemia.

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Conflict of interest statement

Human subjects: Consent was obtained or waived by all participants in this study. Conflicts of interest: In compliance with the ICMJE uniform disclosure form, all authors declare the following: Payment/services info: All authors have declared that no financial support was received from any organization for the submitted work. Financial relationships: All authors have declared that they have no financial relationships at present or within the previous three years with any organizations that might have an interest in the submitted work. Other relationships: All authors have declared that there are no other relationships or activities that could appear to have influenced the submitted work.

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