Endocrine Abstracts

Background: Children with type 1 diabetes mellitus (T1DM) are at increased risk of other autoimmune conditions including thyroid, coeliac and Addison’s diseases. Hyperpigmentation is a recognized feature of Addison’s disease. We present a case with unusual diabetes-technology related hyperpigmentation.

Case report: A 12-year-old male with known T1DM (glutamic acid decarboxylase antibody positive), coeliac disease and autism reported skin darkening at his T-slim insulin pump cannula and Dexcom G6 continuous glucose monitor (CGM) sites. The areas of hyperpigmentation matched the adhesive dressing areas. The skin was not inflamed, hot to touch, raised or tender. Similar areas were visible at previous dressing sites with various shades of brown; he described fading over weeks to months. He had previously been diagnosed with allergic contact dermatitis to the cannula and CGM dressings by dermatology but continued to use them. He also had hyperpigmentation over his knuckles and on the facial skin surrounding his mouth, but not on the buccal mucosa or tongue. There were no symptoms of adrenal insufficiency. He was gaining weight and height, following the 98th and 75th centiles, respectively. His glycaemic control was suboptimal (time in range 42%, HbA1c 66mmol/mol). Notably, he had borderline low plasma sodium (128-132mmol/l) for 12 months. An urgent synacthen test showed a peak cortisol of 370nmol/l with a raised adrenocorticotrophin hormone (ACTH) of 76ng/L, confirming primary adrenal insufficiency. His plasma sodium and potassium were 132mmol/l and 4.8mmol/l, respectively, with an aldosterone of 298pmol/L and renin of 660mU/L, consistent with early mineralocorticoid deficiency. Adrenal antibodies were positive.

Discussion: Hyperpigmentation is recognized to occur in primary adrenal insufficiency due to increased melanocyte stimulating hormone from the formation of ACTH. This typically occurs in the buccal mucosa and skin exposed to pressure, for example the knuckles and skinfolds, and trauma. Hyperpigmentation at sites of diabetes technology adhesives has not previously been described. Localized skin trauma from adhesive dressing removal or, in this case, allergic dermatitis might have contributed. Importantly, hyperpigmentation at sites of diabetes technology dressings should not be assumed to be related to allergic dermatitis; Addison’s disease should be considered, and urgently excluded.