How should I investigate a patient with acanthosis nigricans to assess for underlying insulin resistance or metabolic syndrome?

Acanthosis nigricans (AN) is a cutaneous marker strongly associated with underlying insulin resistance and metabolic syndrome (Napolitano et al., 2015; Karadağ et al., 2018; Leung et al., 2022). To investigate a patient with AN for these conditions, the assessment should include a combination of clinical evaluation and laboratory tests, consistent with the approach for assessing comorbidities in overweight and obese patients ¹.

• Clinical Assessment: This involves measuring the patient's body mass index (BMI) and waist circumference, as well as blood pressure ¹. A thorough medical history should also be taken, including family history of diabetes or cardiovascular disease ¹.
• Laboratory Tests: Essential blood tests include fasting plasma glucose or HbA1c to assess for impaired glucose metabolism or diabetes ¹. A lipid profile, including total cholesterol, HDL cholesterol, and triglycerides, should also be checked to identify dyslipidemia, a component of metabolic syndrome ¹.

While AN is primarily linked to insulin resistance, it is important to note that it can rarely be a paraneoplastic syndrome associated with internal malignancy, though this is less common in the context of assessing for metabolic conditions (Leung et al., 2022).