A 25-year-old man with Acanthosis Nigricans should have which laboratory test ordered?

In the context of Acanthosis Nigricans, which is characterized by dark, velvety patches of skin and is often associated with insulin resistance, a Fasting Blood Sugar (FBS) test is particularly relevant. This patient presentation raises concern for metabolic issues, particularly type 2 diabetes or pre-diabetes, due to the body's reduced sensitivity to insulin.

Ordering a Fasting Blood Sugar allows the healthcare provider to assess the patient's baseline glucose levels after fasting, which helps in determining whether the patient has elevated blood sugar levels consistent with insulin resistance or diabetes. Given the potential metabolic implications of Acanthosis Nigricans, it is critical to evaluate the patient's glucose metabolism.

While a glucose tolerance test or a lipid panel might also be beneficial in a comprehensive evaluation of insulin resistance and metabolic syndrome, the Fasting Blood Sugar is a primary and immediate measure to assess glucose homeostasis, making it the most appropriate initial laboratory test in this scenario.