Insulin edema after initiation of hybrid closed-loop insulin pump therapy with continuous glucose monitoring: a case report

BACKGROUND: Insulin edema is a rare complication which can present after initiation or intensification of insulin therapy in people with diabetes. Initiation of closed-loop hybrid insulin pump therapy can result in rapid improvement in glycemic control for people with diabetes. We present a case in which transition to a closed-loop hybrid insulin pump system, followed by significant improvement in glycemic control, led to development of insulin edema in a person with type 1 diabetes. CASE PRESENTATION: We present a 51-year-old woman with type 1 diabetes of 16 years duration, on insulin pump therapy for more than 10 years, who presented for follow-up 7 weeks after transitioning to a hybrid closed-loop insulin pump system with continuous glucose monitoring (CGM). She complained of weight gain and bilateral lower extremity edema which had started two weeks after the change in pump modality. Laboratory studies and echocardiogram did not reveal any etiology of the acute edema. HbA1c was 3.3% lower than the previous measurement 15 weeks earlier, and there was a significant increase in the daily total insulin dose. With exclusion of other causes of acute edema, the patient was diagnosed with insulin edema and started on hydrochlorothiazide. On follow up, her lower extremity edema significantly improved although her weight did not return to baseline. CONCLUSION: To our knowledge, this is the first case of insulin edema reported in a person with type 1 diabetes using CGM and a hybrid closed-loop insulin pump system. The increase in total daily insulin dose, rapid improvement of glycemic control, and lack of hypoglycemic episodes were important factors to consider in evaluation of this case. Use of hybrid closed-loop systems can help achieve rapid improvement in glycemic control in people with diabetes. This case suggests that consideration should be given to adjusting initial blood glucose targets when starting these remarkable new technologies in people with baseline poor glycemic control.