LBSUN294 Insulin-induced Abdominal Acanthosis Nigricans From High Doses Of Insulin U-500

Abstract

Abstract Introduction Dermatological complications associated with insulin therapy include lipoatrophy, lipohypertrophy, and acanthosis nigricans. We have a rare case of severe acanthosis nigricans from repeated insulin injection. Case A 63-year-old man with diabetes mellitus type 2 presented with an elevated blood glucose of 584mg/dL. He reported "high" glucose levels, despite adherence to his insulin regimen. He only injected insulin in his abdomen. Over 20 years, his insulin doses increased from Lantus 65 units BID and Humalog 35 units TID to Lantus units 110 BID and Humalog 65 units TID. It was later changed to U-500 at 160 units TID. His Hba1c ranged from 10.7% to 15.4%, most recently 13.6%. Physical examination revealed hyperpigmented and thickened plaques, localized to two large areas lateral to his umbilicus. During his hospital stay, insulin was administered on his arms and thighs. Glucose levels improved on Levemir 55 units daily and Lispro 20 units TID. He was discharged on Insulin U-500 40 units TID with instructions to avoid injecting on his abdomen and to rotate injection sites. Discussion Acanthosis nigricans is associated with insulin resistance or hyperinsulinemia. Insulin has a similar structure to insulin-like growth factor (IGF-1). At higher insulin concentrations, it can bind to IGF-1 receptors on keratinocytes and fibroblasts, leading to skin proliferation. Other suggested mechanisms include the involvement of fibroblast and epidermal growth factor. Histopathological findings show hyperkeratosis, papillomatosis, and thickened dermis. Immunochemical findings show positive IGF-1 antibodies in basal epithelial and prickle cell layers. In patients with poor glycemic control and increasing doses of insulin, it is important to assess for insulin-related skin changes. Besides routine visual inspection, skin thickening can be assessed by stroking the skin side-to-side in a sweeping motion instead of palpation. Conclusion Our patient with poorly type 2 diabetes required escalating doses of insulin over the years. He developed severe acanthosis nigricans on his abdomen leading to poor absorption of insulin. This case highlights the importance of routine visual inspection and tactile examination of insulin injection sites for skin changes, as well as repeated counseling regarding insulin site rotation.