Acanthosis Nigricans

Acanthosis nigricans is characterized by the occurrence of velvety brownish skin mainly involving intertriginous areas, or body folds like the neck, axilla, anogenital, and groin areas. In this condition, it should be noted that the pigmentation is not due to increased melanin (pigments synthesized by melanocytes), but because of hyperkeratosis, that means due to abnormal thickening of the outermost layer of the skin.

It may be related to obesity, heredity, diabetes, drug-induced such as Nicotinic acid, OCPs - oral contraceptive pills, and corticosteroids or may be a cutaneous manifestation of some internal malignancy such as adenocarcinoma of the gastrointestinal tract or genitourinary tract or lymphoma.

Acanthosis nigricans starts as pigmentation, dryness, and roughness of the skin with small palpable thickened grain like elevation which gives it a velvety texture.

Types of Acanthosis Nigricans:

Broadly, it can be divided into two types:

1. Benign.
2. Malignant.

Benign Form:

In benign form, skin lesions may be present at birth but usually, develop during childhood or puberty. They may be less severe, involve one side of the body, progress very slowly when compared to malignant one.

Malignant Form:

The lesions are more severe and more extensive. Pigmentation is more prominent and is not confined to thickening of the outermost layer of the skin in skin folds only, but also involves palms, nails, and hair. Irritation is common. The mucous membranes and mucocutaneous junctions are involved in 50 percent of cases, and warty thickening around the lips and eyes are the most common presenting symptoms. Removal of the tumor may be associated with regression of the clinical sign.

Treatment:

• Lifestyle modifications like regular exercise, low-calorie diet and reducing weight if obese.

• The areas need to be cleaned regularly while bathing with cotton balls or loofah.

• Topical retinoic acid (0.025% or 0.1%) either alone or in combination with salicylic acid and lactic acid in an emollient base applied daily at night for two to six months help in reducing the intensity of pigmentation as well as thickening of the skin.

• It has to be remembered that melanocytes or melanin has no role to play in the pigmentation. Hence, demelanizing or fairness cream has no use in this condition.

• Topical steroids like Betnovate (Betamethasone) should be avoided as their applications in body folds can lead to atrophic striae and telangiectasia (visible cutaneous blood vessels due to thinning of the skin).

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