(1.16) Acanthosis Nigricans Complicating Same-Site Repetitive Insulin Injections

Thursday, May 9, 2024

10:25 AM – 10:40 AM CDT

Location: ePoster Showcase, Empire Ballroom Foyer, Level 2

Submitter(s)

MJ

Michael Jakoby, IV, MD

Professor of Medicine and Chief
Southern Illinois University School of Medicine
Springfield, Illinois, United States

Introduction : Acanthosis nigricans (AN) is a hyperkeratotic dermatosis characterized by hyperpigmented, velvety plaques that may occur anywhere but is most frequently observed on intertriginous skin of the dorsal cervical neck, axillae, below the breasts, and groin. AN commonly arises in conditions characterized by significant insulin resistance including obesity, metabolic syndrome, and type 2 diabetes mellitus (DM2). Though rare, AN may also occur at sites of subcutaneous insulin administration. We present a case of AN occurring at the sites of repetitive, high dose insulin injections on the anterior abdomen.

Case(s) Description :

A 70-year-old male with DM2 was referred due to a “rash” at sites of insulin administration. He reported taking 680 units of U500 insulin and 80 units of insulin glargine U300 daily and administering all doses in periumbilical skin. Examination was notable for a discrete hyperpigmented, verrucous plaque surrounding the umbilicus that appeared to be AN but with no other areas of affected skin. Histological findings on biopsy of the affected area included papillomatosis and hyperkeratosis characteristic of AN. The patient was advised to administer insulin remote from the site of AN and rotate to different sites for insulin administration frequently. Modest improvement in AN occurred over the next three months, with more significant improvement in the subsequent six months after the AN was treated with a keratolytic lotion (0.025% tretinoin).

Discussion : While AN is reported in approximately 35% of patients with DM2 in some series, AN at sites of insulin injections is mostly documented in the case report literature. The pathophysiology of AN is poorly understood, though in the setting of insulin resistance and hyperinsulinemia (e.g., obesity), insulin-mediated activation of IGF-1 receptors is felt to stimulate keratinocyte and fibroblast proliferation, leading to the characteristic skin changes of AN. In cases of insulin injection induced AN, repeated exposure to insulin in the subcutaneous space likely leads to activation and proliferation of keratinocytes and fibroblasts in local dermis. Though this patient had extensive AN at sites of insulin injections, he did not have AN at more commonly affected sites such as dorsal cervical skin even though his DM2 was treated with over 750 units of insulin daily. As in most reported cases, administration of insulin at sites other than affected skin was insufficient alone to significantly improve AN. This patient illustrates the importance of discussing insulin administration when skin changes are reported at sites of insulin injections and recognizing that highly repetitive insulin injections are a potential cause of AN.