Acanthosis Nigricans
Basics
Description
- Acanthosis nigricans (AN) is a benign dermatosis characterized by velvety, hyperpigmented, hyperkeratotic plaques, which
- Are usually symmetric
- Most often occur on the posterior neck, flexural and intertriginous surfaces (axilla, elbow, inframammary areas, groin and anogenital regions), and sometimes in mucocutaneous areas
- Are most often asymptomatic but may cause pruritus
- Typically a sign of hyperinsulinemia and insulin resistance but can be a marker of malignancy
- Individuals with AN are at risk of developing metabolic syndrome.
- Etiologies include obesity, insulin resistance, genetic syndromes, familial AN, malignant AN, and drug reactions (1).
Epidemiology
- AN is more common between the ages of 11 and 40 years and in those with body mass index (BMI) ≥30.
- It is more common in individuals with diabetes or risk factors for diabetes.
- It may be a useful indicator of risk of diabetes mellitus (2) and subclinical atherosclerosis (3).
Prevalence
- Prevalence of AN in unselected populations varies from 7% to 74% according to age, race, frequency of type, degree of obesity, and concomitant endocrinopathies (2).
- It is more prevalent in Hispanic, African American, and Native American individuals compared to white or Asian individuals (1).
- In a study of 89 African Americans with AN, there was a 21.3% frequency of DM2 (2).
Etiology and Pathophysiology
- Obesity induced (pseudo-AN) and insulin resistance (2)
- Are the most common etiologies of AN
- More prevalent in individuals with BMI >30. It is weight dependent and may regress with weight loss.
- Higher prevalence of AN in individuals with more risk factors for diabetes and those with type 2 diabetes
- Other endocrinopathies associated with AN include polycystic ovarian syndrome (PCOS), acromegaly, and Cushing syndrome; thyroid diseases; hirsutism; and Addison disease.
- Syndromic AN (1)
- Genetic disorders characterized by insulin resistance can also present with AN. Examples include Down syndrome, leprechaunism, congenital generalized lipodystrophy, and familial partial lipodystrophy.
- Familial AN (1)
- Autosomal dominant mutation of the fibroblast growth factor receptor 3 gene
- Lesions are usually seen in early childhood.
- Malignant AN (1)
- A rare cause of AN characterized by
- Sudden onset, rapid progression, and more extensive lesions
- Presents in atypical locations such as in the mucosa, palms, and soles
- It usually presents in older adults who are often not obese.
- 90–95% are associated with abdominal cavity adenocarcinomas.
- A rare cause of AN characterized by
- May also present with other cutaneous disorders representing internal malignancy such as Leser-Trélat sign (sudden onset of multiple seborrheic keratosis) or tripe palms (ridged velvety lesions of the palms)
- Drug-induced AN (1)
- A rare cause that can be seen with drugs that promote hyperinsulinemia such as systemic glucocorticoids, insulin, oral contraceptives (OCPs), niacin, testosterone, and protease inhibitors
- Lesions usually regress after discontinuation of these drugs.
Genetics
High levels of insulin stimulate epidermal keratocytes and dermal fibroblasts via insulin-like growth factor receptors (IGF-1). The keratocyte proliferation leads to skin changes like papillomatosis and hyperkeratosis (4).
Risk Factors
General Prevention
Encourage diet and exercise to all age groups to reduce likelihood of insulin resistance syndrome.
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Citation
Domino, Frank J., et al., editors. "Acanthosis Nigricans." 5-Minute Clinical Consult, 34th ed., Wolters Kluwer, 2026. Medicine Central, im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688503/all/Acanthosis_Nigricans.
Acanthosis Nigricans. In: Domino FJF, Baldor RAR, Golding JJ, et al, eds. 5-Minute Clinical Consult. Wolters Kluwer; 2026. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688503/all/Acanthosis_Nigricans. Accessed July 16, 2025.
Acanthosis Nigricans. (2026). In Domino, F. J., Baldor, R. A., Golding, J., & Stephens, M. B. (Eds.), 5-Minute Clinical Consult (34th ed.). Wolters Kluwer. https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688503/all/Acanthosis_Nigricans
Acanthosis Nigricans [Internet]. In: Domino FJF, Baldor RAR, Golding JJ, Stephens MBM, editors. 5-Minute Clinical Consult. Wolters Kluwer; 2026. [cited 2025 July 16]. Available from: https://im.unboundmedicine.com/medicine/view/5-Minute-Clinical-Consult/1688503/all/Acanthosis_Nigricans.
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