This obese 18-year-old has had a brown, scaly rash for 4 years. Over that time, the rash has spread from his neck, where it initially developed, to his chest and back. It is asymptomatic but of significant concern. The teen’s obesity has been an issue since early childhood. He has been well otherwise. He has no family history of similar skin changes or diabetes.
His family has consulted a number of physicians. A skin biopsy specimen showed papillomatosis, acanthosis, and increased melanin; there was no evidence of inflammation. Application of a variety of skin creams has resulted in no change in the condition.
What is this rash—and might its appearance and the patient’s clinical history suggest the cause?