Type B insulin resistance syndrome coexisting with aplastic anemia responsive to early immunosuppressive therapy

Type B insulin resistance syndrome (IRS) is a rare autoimmune disorder characterized by severe insulin resistance caused by autoantibodies against the insulin receptor. Clinically, it presents with fluctuating hyperglycemia and hypoglycemia and is frequently associated with other autoimmune diseases. We report a case with the rarely reported combination of type B IRS and aplastic anemia. A 77-year-old woman with obesity presented with abrupt deterioration of glycemic control and bilateral lower extremity edema. Despite the administration of up to 300 units/day of insulin after hospitalization, hyperglycemia remained refractory. Markedly elevated insulin receptor autoantibody titers (85.9%) confirmed the diagnosis of type B IRS. Further evaluation for concomitant pancytopenia revealed aplastic anemia on bone marrow examination. Immunosuppressive therapy with cyclosporine and eltrombopag for aplastic anemia improved the hyperglycemia; however, early morning hypoglycemia, renal dysfunction associated with intravascular volume depletion, and persistent lower extremity edema remained unresolved. The addition of glucocorticoid therapy resulted in rapid clinical improvement and marked reduction in the insulin receptor autoantibody titers (8.6%). This case highlights the importance of early and appropriate immunomodulatory therapy to achieve remission in type B IRS, particularly in patients with multiple concomitant autoimmune diseases.