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Acanthosis nigricans - Anogenital in
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Acanthosis nigricans - Anogenital in

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Contributors: Kyle Cheng MD, Susan Burgin MD, Belinda Tan MD, PhD, Lowell A. Goldsmith MD, MPH, Benjamin K. Fisher MD
Other Resources UpToDate PubMed


Acanthosis nigricans (AN) is a localized skin disorder manifesting with hyperpigmented, velvety plaques typically located in flexural and intertriginous regions. The precise pathogenesis is unknown but is speculated to involve the stimulation of insulin-like growth factor receptors and tyrosine kinase receptors on keratinocytes and fibroblasts.

AN can be classified into 8 types:

I. Obesity-associated – Most common, linked to diabetes, insulin resistance, high body mass index (BMI), metabolic syndrome, polycystic ovarian syndrome (PCOS).

II. Malignancy-associated / cutaneous paraneoplastic syndrome – Most commonly associated with gastric carcinoma, but numerous other malignancies have been reported. Elderly nonobese patients with new AN should have malignancy considered as a cause. Atypical (palmar, perioral, or mucosal) distributions or acute-onset AN may be more associated with malignancy.

III. Drug-induced – Niacin (nicotinic acid) is the most closely associated medication, but AN can also be caused by oral contraceptives, corticosteroids, diethylstilbestrol, heroin, fusidic acid, methyltestosterone, protease inhibitors, and folate.

IV. Syndromic – Type A refers to patients with HAIR-AN (hyperandrogenism, insulin resistance, and acanthosis nigricans) syndrome and acromegaly. Type B is typically seen in women who have uncontrolled diabetes mellitus and autoimmune diseases (systemic lupus erythematosus, scleroderma, Sjögren syndrome, and Hashimoto thyroiditis). This type is associated with the formation of antibodies against insulin receptors.

V. Acral – Affects elbows, knees, and knuckles. Typically seen in healthy sub-Saharan Africans.

VI. Unilateral – Also called nevoid. Usually represents an epidermal nevus in childhood.

VII. Benign – Rare autosomal dominant type developing at birth or during childhood.

VIII. Mixed – Any 2 or more of the above types combined.

Other related endocrinopathies include pituitary hypogonadism, thyroid disease, Addison disease, and acromegaly.


L83 – Acanthosis nigricans

402599005 – Acanthosis nigricans

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Below is a list of drugs with literature evidence indicating an adverse association with this diagnosis. The list is continually updated through ongoing research and new medication approvals. Click on Citations to sort by number of citations or click on Medication to sort the medications alphabetically.

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Last Reviewed:12/05/2016
Last Updated:12/05/2016
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Patient Information for Acanthosis nigricans - Anogenital in
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Acanthosis nigricans is a condition characterized by abnormal thickening and darkening of the skin, especially in body creases. It is most commonly associated with obesity or polycystic ovarian disease in women, though acanthosis nigricans can occasionally be found in people who have more serious underlying health problems or who are taking certain medications. Treatment of the underlying medical condition usually resolves the skin lesions.

Who’s At Risk

Acanthosis nigricans can affect individuals of any age, including children and those of any ethnic background. However, it is more common in adults and in people with darker skin. Males and females are affected equally.

Groups of people who commonly develop acanthosis nigricans:
  • Overweight or obese persons
  • People with endocrine (glandular) abnormalities
  • Persons taking certain medications (for example, oral contraceptives, niacinamide, corticosteroids)
  • Kidney transplant patients
  • People with internal malignancy, especially stomach cancer (very rare cause of acanthosis nigricans)

Signs & Symptoms

The most common locations for acanthosis nigricans include:
  • Sides and back of the neck
  • Armpits
  • Groin
Less commonly, acanthosis nigricans can affect these areas:
  • Face
  • Inner thighs
  • Elbows
  • Knees
  • Navel or belly button
Very rarely, acanthosis nigricans can be found in these locations:
  • Nipples and breasts
  • Eyelids
  • Lips
  • Inside the mouth
  • Anus
The lesions of acanthosis nigricans appear as "velvety" thickenings, and they can range in color from gray to brown to black. Darker-skinned individuals tend to have darker lesions.

Self-Care Guidelines

Because most people who develop acanthosis nigricans are overweight, their skin lesions can improve dramatically and even resolve with weight loss. Other underlying medical conditions should be treated as well.

Other treatments that might help include:
  • Weight loss by changing dietary and exercise habits.
  • Over-the-counter preparations containing alpha-hydroxy acids, such as glycolic acid or lactic acid.
  • Over-the-counter lotions containing salicylic acid.
  • Over-the-counter creams containing urea.
  • Over-the-counter cortisone cream (if the areas are itchy).

When to Seek Medical Care

If you notice thickening and darkening of the skin folds, it is probably a good idea to see your primary care provider. If the acanthosis nigricans is due to obesity, then you can have medical assistance developing healthy strategies to attain your weight goals.

The sudden development of widespread acanthosis nigricans (involving the skin folds as well as the palms of the hands, the lips, and other, less typical areas) should prompt immediate medical attention. The doctor may be able to diagnose and treat a more serious underlying medical condition that is causing the acanthosis nigricans.


The doctor will certainly try to establish the underlying cause of the acanthosis nigricans. If it is due to obesity, then assistance with weight loss may be in order. If obesity is not a factor, the physician may try to determine an underlying cause by ordering blood work, X-rays, or other diagnostic tests.

Once the underlying medical condition has been established and is being treated, your physician may recommend a topical cream or lotion containing the following:
  • Prescription-strength alpha- or beta-hydroxy acids (glycolic acid, lactic acid, salicylic acid)
  • Prescription-strength urea
  • A retinoid such as tretinoin, tazarotene, or adapalene
For more severe, stubborn acanthosis nigricans, oral treatments may include:
  • Dietary fish oils
  • Isotretinoin, a very strong medication with many potential side effects, usually used in the treatment of severe, scarring acne
Not usually covered by insurance, some procedures to treat acanthosis nigricans include:
  • Dermabrasion, a mechanical process of controlled, surgical scraping of the skin
  • Lasers that thin the skin by destroying the uppermost layers


Bolognia, Jean L., ed. Dermatology, pp.712-115, 1717. New York: Mosby, 2003.

Freedberg, Irwin M., ed. Fitzpatrick's Dermatology in General Medicine. 6th ed, pp. 1652, 1796. New York: McGraw-Hill, 2003.
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Acanthosis nigricans - Anogenital in
See also in: Overview
A medical illustration showing key findings of Acanthosis nigricans : Axilla, Hyperpigmented patch, Neck
Clinical image of Acanthosis nigricans - imageId=40959. Click to open in gallery.  caption: 'Acanthotic, thickened, ridged, and hyperpigmented plaques on the posterior neck.'
Acanthotic, thickened, ridged, and hyperpigmented plaques on the posterior neck.
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