Exogenous insulin antibody syndrome in a patient with diabetes secondary to total pancreatectomy

Exogenous insulin can induce insulin antibodies that have a low affinity/high binding capacity. Similar to what is observed in insulin autoimmune syndrome, these insulin antibodies can cause fasting hypoglycemia and postprandial hyperglycemia, a phenomenon known as “exogenous insulin antibody syndrome” (EIAS). Cases of EIAS in patients with type 1 and type 2 diabetes have been sporadically reported, mainly in Asia. However, there has been no report on EIAS in patients with diabetes secondary to total pancreatectomy treated with insulin analogs. A 74-year-old man with diabetes after total pancreatectomy had been treated with continuous subcutaneous insulin infusion using an insulin analog, lispro, and developed recurrent early morning hypoglycemia even after discontinuation of nocturnal basal insulin. His fasting serum lispro level was high even approximately 9 h after the last lispro dose. He had a high titer (72.7%) of insulin antibodies, and a Scatchard analysis revealed low affinity/high binding capacity. These findings suggested that the patient’s recurrent early morning hypoglycemia was associated with insulin antibodies against lispro, and we, therefore, switched from lispro to another insulin analog, glulisine. His hypoglycemia improved, accompanied by a dramatic decrease in his insulin antibodies and serum glulisine levels. Early morning hypoglycemia in patients with diabetes secondary to total pancreatectomy may often be explained by high glycemic variability, malnutrition, and/or glucagon deficiency. However, in cases of recurrent early morning hypoglycemia, EIAS should be considered as a potential differential diagnosis.