Type B Insulin Resistance Syndrome: A Rare Cause of Hypoglycemia.

We describe a case of a Black female patient with a history of type 2 diabetes mellitus and systemic lupus erythematosus, who had a subacute onset of severe hypoglycemia that persisted after cessation of insulin therapy. Biochemical testing revealed hyperinsulinemic hypoglycemia, normal serum triglycerides, and high-normal serum adiponectin levels. Abdominal imaging demonstrated an 11-mm cystic pancreatic lesion. Her clinical history and biochemical test results raised suspicion for type B insulin resistance syndrome (TBIRS), which was confirmed on anti-insulin receptor antibody testing. The patient's hypoglycemia was managed with dietary modification therapy and continuous glucose monitoring. The severity and frequency of hypoglycemic episodes decreased spontaneously. We describe TBIRS and its uncommon hypoglycemic presentation, analyze factors that put TBIRS among the differential diagnosis, and discuss the treatment of TBIRS-associated hypoglycemia.