Acanthosis nigricans is a skin disorder that results
in velvety, light-brown-to-black markings that can occur in any location but
mainly are found in the skin folds of the neck, armpits, groin, and under the breasts.
What causes acanthosis nigricans?
Acanthosis nigricans can affect otherwise healthy
people, or it can be associated with certain medical conditions. Sometimes
acanthosis nigricans is congenital (something a person is born with). It is more
likely to be seen in people with darker skin. The most common type is found in
conditions that are associated with an elevated insulin blood level, such as in
diabetes and obesity. There are many other possible causes of acanthosis
nigricans, including:
- Addison disease, a condition caused by a deficiency of hormones from the adrenal gland
- Disorders of the pituitary gland within the brain
- Growth hormone therapy
- Hypothyroidism (low levels of thyroid hormone caused by decreased activity of the thyroid gland)
- Oral contraceptives
- Some cholesterol medications, including nicotinic acid
Most people with acanthosis nigricans have an insulin
level that is higher than that of people of the same weight who don't have
acanthosis nigricans. Eating too much of the wrong foods, especially starches
and sugars, and being overweight can raise insulin levels.
Rarely, people with certain types of cancer can also develop severe cases of acanthosis nigricans.
How is acanthosis nigricans diagnosed?
The condition can be diagnosed by a doctor through
a medical history and physical examination. Blood work might be done to
investigate the cause of acanthosis nigricans. Occasionally a skin biopsy is
performed to get a detailed look at the tissue in a laboratory.
How is acanthosis nigricans treated?
The most effective treatment is obtained through
weight loss and exercise. Eating a healthy diet can help reduce circulating
insulin and can lead to improvement, and sometimes resolution, of the skin problem.
Other treatments to improve skin appearance, including
Retin-A, urea, alpha hydroxy acids, and salicylic acid prescriptions, may be
helpful in some people. Dermabrasion or laser therapy may help to reduce the
bulky portion of the affected skin.
Acanthosis nigricans caused by medicine may go away once the medication is stopped.
Can acanthosis nigricans be prevented?
When acanthosis nigricans is related to obesity,
weight management is an important part of prevention. A diet that contributes to
reduced insulin also can help prevent acanthosis nigricans.
Other preventive strategies include treating medical
problems that are linked to acanthosis nigricans (such as hypothyroidism) and
avoiding medications that tend to cause or worsen the condition (like oral contraceptives).
References
Van Hattem S, Bootsma AH, Thio HB. Skin manifestations of diabetes. Cleveland Clinic Journal of Medicine. 2008; 75 (11): 772-787
Habif TP. Acanthosis nigricans. In: Habif TP, ed. Clinical Dermatology. 5th ed. Philadelphia, Pa: Mosby Elsevier; 2009:chap 26.
Wolff K, Johnson RA, "Section 5. Miscellaneous Epidermal Disorders" (Chapter). Wolff K, Johnson RA: Fitzpatrick's Color Atlas & Synopsis of Clinical Dermatology, 6e:
www.accessmedicine.com.
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