Case Description: A lean, 17-year-old Caucasian male with type 1 diabetes diagnosed at age 9 experienced an abrupt increase in his insulin requirements. He was managed on mixed daily injections. Daily insulin requirements increased from 1.7 units/kg/day to 3.3 units/kg/day over 6 months. His total insulin level was 7 mcIU/mL with a free insulin level of 4.8 mcIU/mL, indicating exogenous insulin antibodies. Switching from insulin aspart to glulisine, due to presumed antibodies against insulin aspart was unsuccessful, and his insulin requirements continued to increase to 4.4 units/kg/day. Immunosuppressive therapy was commenced with mycophenolate mofetil, decreasing his insulin requirements to 1.1 units/kg/day after 7 months of treatment. Repeat testing revealed an improvement in the discrepancy between total and free insulin levels, with a total insulin level of 5.2 mcIU/mL and free insulin level of 4.6 mcIU/mL.

Discussion: Exogenous insulin antibody syndrome should be considered in patients with poorly controlled diabetes and requiring greater than 2 units/kg/day of insulin without obesity. Classically, antibodies against exogenous insulin were found in patients receiving insulin derived from animal sources; however, recombinant human insulin can very rarely trigger an antibody response in select patients. Immunosuppression using mycophenolate mofetil greatly reduced insulin requirements and this case highlights its novel use in children with diabetes who develop insulin antibody syndrome.


L. Saba: None. A. B. Orandi: None. S. Pittock: None. A. Creo: None.

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