Context: Insulin autoimmune syndrome (IAS), or Hirata's disease, is a rare hypoglycemic disorder characterized by spontaneous hypoglycemia without evidence of exogenous insulin administration, a high serum concentration of total immunoreactive insulin, and the presence of insulin autoantibodies in high titer. The majority of cases occur in the Asian population, and treatment is generally successful with watchful waiting or steroids. Case Description: We report the case of a 71-year-old

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... man with severe hypoglycemia due to IAS that was refractory to a prolonged course of high-dose steroids. Type 1 diabetes prevention trials using rituximab have shown selective suppression of insulin autoantibodies, which are the pathogenic antibodies in IAS, and therefore we provided this therapy. Treatment with two doses of rituximab and daily use of a continuous glucose monitor resulted in disease remission. Conclusion: We present the first case where potentially life-threatening hypoglycemia due to IAS was successfully managed with rituximab and a continuous glucose monitor. We conclude that these treatment modalities are effective for the management of severe, refractory IAS. (J Clin