A Case of Insulin Autoimmune Syndrome Complicated by IgG4-Related Disease, Both Successfully Treated with...

We present the case of a 73-year-old man diagnosed with insulin autoimmune syndrome (IAS) during an investigation of hypoglycemia. This disease is a rare cause of hypoglycemia induced by autoantibodies against insulin. The patient was diagnosed with IgG4-related disease (IgG4-RD). Moreover, the patient had myelodysplastic syndrome (MDS). We hypothesized that immunological dysregulation driven by MDS may have contributed to the coexistence of these two rare conditions in our patient. Treatment with prednisolone promptly resolved hypoglycemia and improved the disease activity of IgG4-RD. We present this case as, to the best of our knowledge, it is the first peer-reviewed case report of coexisting IAS and IgG4-RD.