Exogenous Insulin Antibody Syndrome (EIAS) Presenting in an Elderly, Long-Term Patient with Type 1 Diabetes Mellitus that Resolved with Low-Cost Outpatient Therapy with Mycophenolate Mofetil and Regular Insulin by Pump

Exogenous insulin antibody syndrome (EIAS) has until recently been a rarely described complication of exogenous insulin therapy. EIAS results not only in hyperglycemia, but also in hypoglycemia and occasionally in ketoacidosis (DKA). The incidence of EIAS is increasing probably due to an overall increase in autoimmunity associated with the coronavirus disease 2019 (Covid-19) epidemic resulting in increasing binding of insulin by antibodies. Herein, we describe a case of EIAS occurring in an elderly patient with longstanding type 1 diabetes mellitus (T1DM) who had progressive loss of glycemic control. It responded positively, as we have previously described, to oral mycophenolate mofetil and the use of soluble regular insulin delivered by continuous subcutaneous insulin infusion (CSII). Therefore, EIAS is an increasingly frequent cause of hyperglycemia with and without DKA, and hypoglycemia in subjects with T1DM. Once diagnosed, they can be treated with mycophenolate mofetil and soluble insulin in an outpatient setting, which will decrease the rate of hospitalization and lower the expense of therapy.