Antibody-Mediated Extreme Insulin Resistance: The Importance of Pre-Treatment Screening

We report the case of a 56 year-old Hispanic male with a 10-year history of type 2 diabetes who presented with abrupt onset of hyperglycemia resistant to escalating doses of intravenous insulin infusion (>2500 units daily). He was diagnosed with antibody-mediated insulin resistance given the presence of hyperglycemia despite receiving >200 units insulin/day, a lack of identifiable precipitants for diabetic ketoacidosis or hyperosmolar hyperglycemic state, and elevated insulin antibodies. He underwent pre-immunomodulatory therapy screening for infections, rheumatologic disorders, and malignancy, which uncovered a new diagnosis of latent tuberculosis. While concurrently being treated for latent tuberculosis, he successfully responded to immunomodulatory therapy with rituximab, dexamethasone, and cyclophosphamide. Insulin was discontinued completely, and he maintained appropriate glycemic control on oral diabetic agents (metformin and pioglitazone). This case supports the use of immunomodulatory therapy for the treatment of antibody-mediated insulin resistance and highlights the importance of pre-immunomodulatory therapy screening to uncover occult infection or identify underlying neoplastic/rheumatologic disease prior to immunosuppression.