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Acanthosis Nigricans

Definition

Acanthosis nigricans is a skin condition in which brown or black velvet-like markings appear under the arms, in the groin, or on the back of the neck. Any skin fold can be affected, including the lower lip and chin.

Causes

Causes of acanthosis nigricans may include:

  • High insulin levels in people who are obese
  • A family history of acanthosis nigricans
  • A cancerous tumor (rarely)

Risk Factors

Risk factors that increases your chance of getting acanthosis nigricans include:

  • Being overweight
  • Type 2 diabetes
  • Polycystic ovary syndrome (PCOS)
  • Heredity: People of African-American descent are more likely to develop acanthosis nigricans

Symptoms

If you experience any of these symptoms, do not assume it is due to acanthosis nigricans. These symptoms may be caused by other health conditions.

  • Velvety-looking, dark areas on:
    • Back of the neck
    • Armpits
    • Groin
    • Elbow
    • Knees
    • Knuckles
    • Face
    • Palms

Diagnosis

Your doctor will ask about your symptoms and medical history. A physical exam will be done. Tests may include the following:

  • Skin biopsy
  • Blood tests
  • Imaging tests such as X-rays or endoscopy to rule out other causes

Endoscopy
Endoscope in stomach
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Treatment

Treatment often involves treating the underlying cause. For example, if acanthosis nigricans is due to obesity, weight loss can improve the skin condition.

Topical and oral retinoids and other medicines have been reported to improve appearance in some cases. They help remove excess layers of skin.

Prevention

The best way to reduce your chances of getting acanthosis nigricans is to maintain a healthy weight through diet and regular exercise.

Resources

National Organization for Rare Diseases
http://www.rarediseases.org/
American Academy of Dermatology
http://www.aad.org/for-the-public/home

Canadian Resources

References

Acanthosis nigricans. EBSCO DynaMed website. Available at: http://www.ebscohost.com/dynamed. Updated December 10, 2010. Accessed November 19, 2012.
Clark N, Stulberg DL, Tovey D. Common hyperpigmentation disorders in adults: part II. Melanoma, seborrheic keratoses, acanthosis nigricans, melasma, diabetic dermopathy, tinea versicolor, and postinflammatory hyperpigmentation. Am Fam Physician. 2003 Nov 15;68(10). Available at: http://www.aafp.org/afp/20031115/1963.html. Accessed November 19, 2012.
Goff DC, Katz AS, Feldman SR. Acanthosis nigricans in obese patients: presentations and implications for prevention of atherosclerotis vascular disease. Dermatology Online Journal. 2000;5(1). Available at: http://dermatology.cdlib.org/DOJvol6num1/original/acanthosis/katz.html. Accessed November 19, 2012.
10/15/2010 DynaMed's Systematic Literature Surveillance http://www.ebscohost.com/dynamed/what.php : Kong AS, Williams RL, Smith M, et al. Acanthosis nigricans and diabetes risk factors: prevalence in young persons seen in southwestern US primary care practices. Ann Fam Med. 2007;5(3):202-208. Kong AS, Williams RL, Rhyne R, et al. Acanthosis Nigricans: high prevalence and association with diabetes in a practice-based research network consortium—a PRImary care Multi-Ethnic network (PRIME Net) study. J Am Board Fam Med. 2010;23(4):476-485.