Granulomatous hypersensitivity to protamine as a complication of insulin therapy

Successful desensitization with human insulin in a patient with an insulin allergy and hypersensitivity to protamine: a case report

Introduction

Insulin allergy may occur in patients treated with subcutaneous applications of insulin preparations. Besides additives in the insulin preparation such as protamine, cresol, and phenol, the insulin molecule itself may be the cause of the allergy. In the latter case, therapeutic options are rare.

Case presentation

A 68-year-old man with poorly controlled type 2 diabetes mellitus received different insulin preparations subcutaneously while on oral medication. Six to eight hours after each subcutaneous application, he developed pruritic plaques with a diameter of >15 cm at the injection sites that persisted for several days. Allergologic testing revealed positive reactions against every insulin preparation and against protamine. Investigation of serum samples demonstrated IgG antibodies against human and porcine insulin. We treated the patient with human insulin using an ultra-rush protocol beginning with 0.004 IU and a rapid augmentation in dose up to 5 IU. Therapy was accompanied by antihistamine therapy. Subsequent conversion to therapy with glargine insulin (6 IE twice daily) was well-tolerated.

Conclusion

As reported in this case, desensitization with subcutaneously administered human insulin using an ultra-rush protocol in patients with an insulin allergy may present an easy form of therapy that is successful within a few days.

Hypersensibilité aux insulines

GREAT PROGRESS: The use of purified insulins obtained by genetics has dramatically lowered the frequency of insulin hypersensitivity. This frequency has decreased from 1 to 55% with non purified insulins and to 0.1 to 2% with newly generated insulins.

DIAGNOSTIC MEASURES

The anamnesis should clarify the allergic background of the patient, previous treatments with insulin, their duration of use and any eventual reactions. Examination of the lesions must assess the type (papule, eczema, purpura), the localization and extent. The second step skin tests, when negative, eliminate the responsibility of the insulin tested. They also participate in the search for cross-reactions between the various insulines. Their positivity is not always synonymous of hypersensitivity. STRATEGY TO BE APPLIED: In the case of localised cutaneous reactions, spontaneous regression is generally observed, the association of an oral antihistamine and/or the fractioning of the dose and its injection on several different sites often leads to the disappearance of these reactions. If the reactions persist, topical or oral corticosteroids of short duration can be useful. Finally, the switch to another insulin or even a tolerance induction with the least skin test reactive insulin as a last resource. The most severe systemic reactions are an indication for tolerance induction.