EVALUATION AND MANAGEMENT OF DELAYED HYPERSENSITIVITY REACTION TO INSULIN IN

Abstract

<h3>Introduction</h3> Type I hypersensitivity to insulin is rare. In most adverse reactions to insulin, additives, excipients, or preservatives are implicated, resulting in type III or IV hypersensitivity. We describe an adolescent patient with delayed type hypersensitivity to insulin and discuss evaluation and management strategies. <h3>Case Description</h3> A 16-year-old female with type I diabetes mellitus used an insulin pump without problems for 6 years. Recently, she began to develop a delayed, itchy, painful pump site rash. Symptoms were managed with pump site rotation, trials of various insulins, trials of return to manual insulin injections, and oral antihistamines. A variety of allergy testing—percutaneous, intradermal, and patch—has been largely negative, suggesting against type I and IV hypersensitivities. Punch biopsy of the rash was performed with basic pathology and various stains completed, consistent with type IV hypersensitivity. Table 1 shows test results. <h3>Discussion</h3> Type III hypersensitivity was the leading differential diagnosis given some delayed intradermal positive results, negative patch testing, and previous positive serum IgG to insulin; however, biopsied tissue did not show immune complex deposition. The pathology was more consistent with a type IV hypersensitivity. Little is known about effectively managing these delayed hypersensitivity reactions as insulin therapy continues. Our patient started adjunctive metformin therapy and will undergo additional, extensive patch testing with Dermatology. Other therapies to consider include low-dose corticosteroid co-infusion with insulin and/or biologic drug therapy. It is important to distinguish that these patients do not have insulin allergy but may require support from an allergist to facilitate comfortable receipt of chronic diabetes treatment.