Endocrine Abstracts

We present a 52-year-old female with a 26-year history of type-2 diabetes mellitus who has been difficult to treat owing to the development of multiple insulin allergies. She initially developed local hyperpigmentation and itchy swellings at the injection sites of her Humulin I in 2016, with similar symptoms occurring when she was switched to NovoRapid. Additionally, she developed one severe, systemic reaction to Humulin I. All insulin treatment was stopped, and she was left solely on oral agents. The patient was referred to an allergy specialist: specific IgE to insulin was found to be raised at 3.39 kUA/l, and intradermal testing was positive to nearly all insulins tested. The only negative intradermal test was to Hypurin Bovine Lente, the only insulin not to contain the excipient metacresol. It is therefore likely that her allergy is actually to metacresol as opposed to insulin per se, but she has not yet been challenged with metacresol alone. To optimise her diabetes control, and known diabetic complications of retinopathy and neuropathic feet, she was started on a regimen of Hypurin Bovine Lente; HbA1c reduced from 121 mmol/mol to 73 mmol/mol over the course of five months. Unfortunately, Hypurin Bovine Pente will not be available in the United Kingdom for much longer. Patients with diabetes requiring insulin who have an insulin allergy are rare, but there are multiple reported cases. In contrast to our case, allergy is usually to bovine or porcine insulins and thus its incidence has decreased since the advent of human insulins. There is no obviously superior management option, and a patient-specific approach is needed. Successful managements reported in case literature vary from specific immunotherapy, to desensitisation regimes and continuous subcutaneous insulin infusion. We plan to challenge our patient with Insuman Infusat and refer her for potential bariatric surgery.