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, which means due to abnormal thickening of the outermost layer of the skin.
Acanthosis nigricans can occur equally between males and females of all ages, with a slight predilection for people below the age of 40 years. The risk of acanthosis nigricans is twice in patients with type 2 diabetes.
What Causes Acanthosis Nigricans?
Acanthosis Nigricans may be related to obesity, heredity, diabetes, drug-induced such as nicotinic acid, oral contraceptive pills (OCP), corticosteroids, or maybe a cutaneous manifestation of some internal malignancy such as adenocarcinoma of the gastrointestinal tract or genitourinary tract or lymphoma.
How Is Acanthosis Nigricans Presented?
Acanthosis nigricans starts as pigmentation, dryness, and roughness of the skin with a small palpable thickened grain-like elevation, giving it a velvety texture.
Layer tags are found on the skin and mucosal linings.
Sometimes, the lesions can become macerated (moisture-based damage and wrinkled skin).
Irritation and itchiness are often associated with malignant type acanthosis nigricans.
How Do Acanthosis Nigricans Develop and Progress?
The development of acanthosis nigricans has been linked to the levels of growth factors, especially the insulin-like growth factor (IGF) activation.
In benign acanthosis nigricans, the insulin-like growth factor increases the generation of epidermal cells. However, in the case of malignant acanthosis nigricans, the cancer cells act as a stimulating factor.
What Are the Types of Acanthosis Nigricans?
Broadly, it can be divided into two types:
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, and progress very slowly when compared to malignant ones.
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.
Based on the multiple factors associated, the acanthosis nigricans can be named as,
Familial Acanthosis Nigricans:
The condition occurs in an autosomal dominant fashion.
Obesity-associated Acanthosis Nigricans:
Being overweight has been the common cause associated with acanthosis nigricans, which may be due to insulin resistance.
Medications-Associated Acanthosis Nigricans:
Steroids, growth hormones, and Insulin have been related to the development of acanthosis Nigricans.
Acanthosis Nigricans Associated With Endocrine Dysfunction:
Uncontrolled diabetes, androgen hyperactivity, insulin resistance, and polycystic ovarian syndrome (PCOD) patients are more likely to have acanthosis nigricans.
Acral Acanthotic Anomaly:
The lesions of acanthosis nigricans are restricted to particular areas like elbows, knuckles, knees, and the dorsal end of the feet.
Malignant Acanthosis Nigricans Syndrome:
Certain cancers like the prostate, lung, ovary, and breast will cause a rapid onset of acanthosis nigricans.
Auto-Immune Acanthosis Nigricans:
Autoimmune disorders like systemic lupus erythematosus, Hashimoto's thyroiditis, and Sjogren's syndromes are related to acanthosis nigricans.
Unilateral Acanthosis Nigricans:
The pigmentation occurs only unilaterally and is also known as nevoid acanthosis nigricans.
How to Diagnose Acanthosis Nigricans?
A complete medical and family history can guide towards the diagnosis of acanthosis nigricans.
Physical examination may reveal the presence of thick, velvety hyperpigmented patches on the skin, especially in the folds of the groin, axilla, and back neck.
Acanthosis nigricans pigmentation can also be seen in the mucous lining of the nasal cavity, oral cavity, larynx, and esophagus.
Some patients may have eye and nail changes.
Finally, the definite diagnosis of acanthosis nigricans can be made using skin biopsies.
What Are the Treatment Options for Acanthosis Nigricans?
Acanthosis nigricans is basically a symptom depicting an underlying medical condition. The primary aim of the treatment of acanthosis nigricans is to manage the existing disease.
Lifestyle modifications like regular exercise, a low-calorie diet, and reducing weight can keep the lesions under check.
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 helps in reducing the intensity of pigmentation as well as thickening of the skin.
Topical vitamin D analogs can help improve the acanthosis nigricans lesions.
It has to be remembered that melanocytes or melanin have no role to play in pigmentation. Hence, de-melanizing 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).
Melatonin seems to work in obese patients with acanthosis nigricans.
Cosmetic solutions like laser and chemical peels have been used in acanthosis nigricans.
Surgical removal is the only choice in malignant acanthosis nigricans.
What Are the Complications of Acanthosis Nigricans?
The complications of acanthosis nigricans depend on the factors that are involved in the condition.
Cosmetic disturbances in physical appearance.
Emotional and mental distress.
Individual risk factors for the presence of diabetes mellitus.
Malignancy (cancer cells) linked problems.
Other underlying disease-related complications.
Acanthosis nigricans is a rare skin condition. Benign type of acanthosis nigricans resolve faster and have good treatment outcomes. But in the case of malignant type, it will usually have poor treatment outcomes. Therefore, consult a dermatologist immediately when you find signs of acanthosis nigricans. An endocrinologist may be involved in managing acanthosis nigricans, as they are often associated with diabetes and metabolic disorders. Psychological treatment should also be considered as early as possible since patients with acanthosis nigricans suffer from depression and low self-esteem.
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