Hyperpigmented skin

A 43-year-old electronic technician arrived for his annual test. He had no complaints, except for occasional discomfort linked with skin lesions that were symmetrically present in both axillae, as shown in the image below. During history taking, he admitted he has always been overweighting his whole life and having many family members with type 2 diabetes. He has lost his father to colon cancer last year. He hadn't changed the brand of his bath soap, deodorant, or laundry detergent in a long time. He also denied having myalgias, arthralgias, or any skin conditions. He has never smoked but he does drink beer at social gatherings. On examination, the temperature was 37.3 C, the pulse rate was 80/ minute, the blood pressure was 130/85 mm Hg, and the BMI was 29 kg/m². His axillary skin examination revealed velvety, hyperpigmented lesions. The thyroid examination revealed no abnormalities. The laboratory results revealed a borderline increased blood glucose level and a normal complete blood count. Which of the following is the proper diagnosis,