A Skin Story: Acanthosis Nigricans

The skin tells stories far beyond the surface—and for the school nurse, it can offer early clues about what’s happening beneath. One such clue is acanthosis nigricans (AN), a skin condition characterized by dark, thickened, velvety patches, most often on the neck, underarms, or groin. Though it’s sometimes mistaken for poor hygiene—those stubborn “dirty” areas that just won’t wash off—AN is actually a visible sign of insulin resistance and may be an early warning of metabolic imbalance.​

What is it?

At the cellular level, acanthosis nigricans develops when excess insulin in the bloodstream stimulates skin cells to grow more rapidly than usual. This overgrowth causes the skin to become thicker, darker, and slightly textured—changes known medically as hyperkeratosis and papillomatosis. While rare cases in adults can signal internal malignancy, in the pediatric population, AN is overwhelmingly the hallmark of insulin resistance and metabolic syndrome.​

Who does it affect?

The prevalence of this marker acts as a clinical shadow to the steady climb in pediatric obesity, growing more prominent as national weight trends rise. Studies show that among children and adolescents with obesity, about half—between 49% and 58%—exhibit AN, making it a frequent finding in the school health office. Although it can surface at any age, data indicate it’s appearing in students as young as ten, reflecting the earlier onset of metabolic concerns.

This “velvety warning sign” also shows clear demographic patterns—it’s seen more frequently in Native American, African American, and Hispanic students than in White or Asian peers. Because its presence tends to rise with age and puberty, AN can be a valuable, noninvasive indicator for school nurses conducting routine risk assessments or other health screenings, serving as a powerful early clue to insulin resistance and potential type 2 diabetes risk. This quick, noninvasive observation requires nothing more than a keen eye and good lighting to detect the telltale velvety darkening often found along the neck or under the arms.

What do school nurses need to know?

In Texas, this practice carries additional weight—it’s not just a best practice but a state mandate. School nurses in certain regions are required to screen students in designated grades for AN, alongside traditional vision and hearing assessments. School districts across other parts of the country have adopted similar protocols, recognizing the efficiency of school-based diabetes risk identification.

When AN is identified, it’s more than a simple skin finding—it’s a call to action. The next step often includes assessing body mass index (BMI) and blood pressure, as AN frequently occurs as part of a broader metabolic picture that includes obesity and hypertension. The American Diabetes Association has recognized AN as an official risk factor for type 2 diabetes since 2000, but some public health agencies, including the CDC, have raised concerns about the follow-up challenges of large-scale screenings.

Anything else?

Just as important, AN carries social and emotional weight for students. Because these patches are often mistaken for “dirty skin,” students and parents may feel confusion, worry, or even embarrassment. In these moments, the school nurse’s role extends beyond detection to education and encouragement—helping caregivers see AN as a manageable sign of elevated insulin, not a hygiene concern. By sharing clear information and doing everything in their power to ensure follow-up with a primary care provider, the school nurse bridges the gap between school screening and medical care.

Every observation, every conversation, and every reassurance offered in the privacy of the school health office can spark early intervention, healthier habits, and greater health literacy for the entire family. In the hands of a skilled school nurse, early recognition becomes a pathway to lifelong health for each and every student.