Protamine allergy as a complication of insulin hypersensitivity: A case report

Background: Although most patients receiving insulin produce insulin-specific IgE, significant allergic symptoms develop in very few of them. Patients receiving neutral protamine Hagedorn (NPH) insulin are at increased risk for the development of protamine hypersensitivity. The case of a 19-year-old woman with insulin-dependent diabetes and regular and NPH insulin hypersensitivity is presented. Objective: The purpose of this study was to determine whether desensitization to NPH insulin, as well as standard insulin desensitization, could control allergic symptoms in a patient allergic to both NPH and regular insulin. Methods: The patient required insulin desensitization for severe urticaria, angioedema, and occasional wheezing resulting from her insulin dose. She underwent a standard protocol for insulin desensitization twice in a 2-month period, with persistence in her symptoms. She was found to have high protamine-specific, as well as insulin-specific, IgE levels, and because of her poor response to regular insulin desensitization, she was desensitized to both regular and NPH insulin. Results: Dual desensitization resulted in marked improvement in her symptoms. The patient had recurrence of urticaria and angioedema a year and a half later, at which point the NPH was stopped and she was desensitized to regular insulin. She continued to receive regular insulin 4 times per day over the following 3 years with only occasional hives. Conclusion: Patients with insulin allergy may not have complete resolution of their symptoms after standard desensitization, particularly those patients with concomitant protamine allergy. These patients may require protamine/NPH desensitization, an alternative insulin preparation, or both.