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Acanthosis nigricans is one of the commonest skin conditions in individuals with rich complexion. It is basically a metabolic disorder in which the skin becomes thickened and pigmented following insulin resistance.

The various underlying causes of acanthosis nigricans are:

1. Genetics

2. Obesity

3. PCOS (Polycystic ovarian syndrome)

4. Thyroid disorders (hypothyroidism)

5. Diabetes

6. Drugs like hormonal pills, nicotinamide

7. Internal malignancies 

Excess insulin causes an increase in the thickness as well as the pigmentation of the skin by means of production of more melanin and more number of skin cells called keratinocytes. This thickening of the skin gives it a dirty, dark appearance making it look brown-black and ‘velvety’.

Since diabetes is quite common in individuals of Asian and African-American descent, acanthosis nigricans is also inevitably commonly seen in these groups. Also, because of polycystic ovarian syndrome/disease, acanthosis nigricans is increasingly being observed in younger women. The widespread prevalence of childhood obesity is additionally giving rise to more and more cases of acanthosis nigricans.

The common sites where acanthosis nigricans show up are the underarms, back and sides of the neck, the front of the elbows and knees as well as around the eyes, mouth and the temples of the forehead. It can also cause darkening of the knuckles.

Prevention and care:

It often looks like a dirty-looking neck which has not been ‘cleaned’. Patients often believe that rubbing and scrubbing these areas will help lighten the pigmentation but in fact this friction actually worsens the pigmentation. Hence, using scrubs, loofahs and other similar physical exfoliation methods must be avoided.

It is equally important to apply sunscreen over the neck (sides and back) as well as the arms and other exposed areas in order to prevent worsening of the existing pigmentation. Sunscreens with SPF 30 are usually sufficient for these areas.

If you have noticed such a pattern of pigmentation at these sites, visit your dermatologist at the earliest so that the underlying cause for the pigmentation can be diagnosed and treated. Rarely, an underlying cancer may present with acanthosis nigricans initially. Treating the underlying cause will often result in resolution of the pigmentation over a period of one to two years.

For example, correcting the underlying diabetes, thyroid issues, PCOS, etc. using hormonal medications will actually bring about an improvement in the skin.

Treatment:

Weight management remains the main management option for acanthosis nigricans. With weight reduction, the pigmentation lessens, the skin appears thinner and any creams applied can penetrate deeper and can show a benefit.

Topical medications used for acanthosis nigricans will contain a combination of keratolytics like urea, ammonium lactate, etc. along with chemical exfoliants such as glycolic acid and lactic acid.

Topical retinoids are also a great option for decreasing the thickness and pigmentation. Tretinoin 0.1% has been frequently used. In order to prevent irritation and photosensitivity, it is important to use sunscreen along with use of retinoids. Rarely, your doctor may want to put you on oral medications like oral retinoids (isotretinoin/Accutane).

References:

  1. Higgins SP, Freemark M, Prose NS. Acanthosis nigricans: a practical approach to evaluation and management. Dermatol Online J. 2008;14(9):2. Published 2008 Sep 15.
  2.  De Sanctis V, Soliman A, Marsciani A, et al. Acanthosis nigricans in adolescents: a practical approach. Georgian Med News. 2013;(222):73-78.