Protamine-containing insulin allergy and renal dysfunction in a patient with type 2 diabetes

An 87-year-old woman with type 2 diabetes noticed a red itchy rash at the insulin injection sites 3 weeks after initiation of premixed insulin therapy. Laboratory data at that time showed marked eosinophilia and progression of renal dysfunction. Insulin treatment was discontinued, and antidiabetic oral drugs were used, as well as intravenous injection of dexamethasone. Her skin lesions disappeared, and both eosinophilia and renal dysfunction gradually improved. The results of skin prick tests and measurement of specific immunoglobulin E antibodies suggested that the insulin allergy was caused by protamine. Although cases of insulin allergy associated with renal dysfunction are rare, we must be aware, especially for elderly patients with poor renal function in the first application of insulin.