Abdominal wall pigmentation
He had been administering insulin injections into his abdominal wall skin but was not rotating injection sites and had induced localised acanthosis nigricans. Pseudoacanthosis nigricans is commonly seen in diabetics and prediabetics who have high insulin levels leading to epidermal thickening in these areas.
In this man the large amount of locally injected insulin led to proliferation and pigmentation of the overlying epidermis. He needs to rotate his injection sites. For histology, log into www.skinconsult.com.au