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.