Acanthosis Nigricans Independent Risk Factor for Type 2

Acanthosis nigricans is an independent risk factor for type 2 diabetes, and its presence may help primary care clinicians identify high-risk patients with diabetes sooner, according to the results of a cross-sectional study.

"Evidence shows acanthosis nigricans is often associated with hyperinsulinemia and may indicate increased risk of type 2 diabetes mellitus," write Alberta S. Kong, MD, MPH, from the University of New Mexico School of Medicine in Albuquerque, and colleagues from Research in Outpatient Settings Network. "The purpose of this study was to determine the association of acanthosis nigricans with type 2 diabetes risk factors and disease in young persons."

At the Research in Outpatient Settings Network, a practice-based research network in southwestern US communities, 96 participating clinicians collected data on 1133 children and adolescents (aged 7 – 19 years) and young adults (aged 20 – 39 years) who were seen during a 2-week sampling period. Primary endpoints were the prevalence of acanthosis nigricans, type 2 diabetes risk factors (ethnicity, family history of type 2 diabetes, hypertension, and overweight/obesity), type 2 diabetes, and the relationships among these.

Risk factors for type 2 diabetes were common in this sample: 69% had a family history of type 2 diabetes, 3% of children/adolescents and 12% of adults had hypertension, 43% of children/adolescents and 73% of adults were overweight or obese, and 80% were members of ethnic minorities.

Acanthosis nigricans was identified in 17% of children/adolescents and in 21% of adults. For both age groups, the more type 2 diabetes risk factors that were present, the higher the prevalence of acanthosis nigricans (P < .001). In patients with acanthosis nigricans, the prevalence ratio for type 2 diabetes was 1.97 (95% confidence interval, 1.18 – 3.27; P = .01), after controlling for age, body mass index, and the number of type 2 diabetes risk factors.

Clinicians noted that identifying acanthosis nigricans often allowed discussions about lifestyle modification to decrease the risk for type 2 diabetes.

"Patients with acanthosis nigricans are likely to have multiple risk factors for type 2 diabetes," the authors write. "Acanthosis nigricans may be an independent risk factor for this disease. Detection of acanthosis nigricans may help clinicians more rapidly identify high-risk individuals for diabetes counseling."

"Detection of acanthosis nigricans may also enhance patient and clinician receptivity to discussing risk reduction for type 2 diabetes," the authors conclude.

Practice Pearls

• Acanthosis nigricans is a thickening and darkening of the skin that usually occurs in the axilla and neck. It has been associated with certain neoplasms as well as hyperinsulinemia.
• The current study demonstrates that acanthosis nigricans may be an independent risk factor for type 2 diabetes.

Ann Fam Med. 2007;5:202-208.

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