SAT155 Insulin Receptor Autoantibody Syndrome (Iras): A Rare Occurrence In Lymphoproliferative Disease

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Abstract Disclosure: C. Villatoro Santos: None. E.A. Oral: None. Insulin receptor antibody syndrome (IRAS) may present as fasting hypoglycemia, high serum insulin, and serum autoantibodies to insulin receptor at low titers. We present a case of a patient with multiple myeloma (MM) who developed hypoglycemia suspected to be related to insulin receptor antibodies. The patient is a 60-year-old male with history of prediabetes, MM, anemia, and thrombocytopenia treated with carfilzomib, dexamethasone 20 mg weekly, and prior radiation to the right pelvis, who presented to the hospital for increased right hip pain and cough. Patient reported 4 days of markedly decreased appetite with poor intake. He noted increased chronic right hip and low back pain. On exam, he was cachectic, had hyperpigmentation under bilateral eyes, and muscle wasting. Hypoglycemia as low as 38 mg/dL (70-180 mg/dL) was noted. MM studies on hospital day 4 showed increased kappa-M protein and kappa-free light chains with worsening anemia and thrombocytopenia, concerning for progression of his disease. He later developed recurrent hypoglycemia; endocrinology was consulted on hospital day 6. He also had hyponatremia and borderline low blood pressure. Cortisol on hospital day 7 at 9:00 am was 15.4 μg/dL (5.3-22.5 μg/dL) in the setting of normoglycemia. On hospital day 9, hematology started dexamethasone 40 mg daily for 3 days for MM relapse, which resulted in marked improvement in his mental status, appetite, and resolution of hypoglycemia. On hospital day 11, he started weekly cyclophosphamide, bortezomib, plus dexamethasone for 3 weeks. Results for hypoglycemia workup returned on hospital day 12 from samples of Day 7: glucose 53 mg/dL (70-180 mg/dL), C-peptide 0.2 ng/mL (1-5.2 ng/mL), insulin 14.6 μU/mL (1-21 μU/mL), insulin antibodies undetectable, negative serum screen for oral hypoglycemic agents. His course was complicated by sepsis with gram-negative bacteremia treated with antibiotics and stress dose hydrocortisone. He was discharged to rehab on hospital day 34 on dexamethasone 4 mg daily. Glucose, c-peptide and insulin levels could be consistent with exogenous hyperinsulinemic hypoglycemia but may also represent delayed insulin clearance due to insulin receptor antibodies and autocrine suppression of pancreatic insulin production in a patient with no access to insulin. Therefore, the most likely diagnosis was IRAS. The insulin antibody radioactive essay was negative for native IgG and IgM antibodies; testing for insulin receptor antibodies is in progress as a clinical test is unavailable. Treatment is common with high doses of steroids. IRAs can be seen in patients with lymphoproliferative disorders and would respond to steroid treatment for hospital management. Definitive treatment should be tailored with oncology guidance. There is a need for an accessible clinical test for IRAS in the US. Presentation: Saturday, June 17, 2023