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Acanthosis nigricans (AN) is a common skin condition characterised by thickening (hyperkeratosis) and darkening (hyperpigmentation) of the skin with a velvety texture. To mention, AN is not a skin disease but its occurrence may indicate an underlying disease. This disorder of the skin often affects folded areas of the body like neck, armpits, groin, elbows, knuckles, palms and knees  .
AN is common in both men and women, especially in people who are obese, have diabetes or are prediabetics, have darker skin or belong to areas where the prevalence of darker skin is more like Africa and the Caribbean  . It can also be a sign of underlying tumour which may be benign or malignant. A malignant (cancerous) form of AN usually occurs in people above the age 40 while the benign (noncancerous) AN is evident during childhood. Also, if AN is present from childhood, there's a huge possibility that the child may develop diabetes in the coming years.
Causes Of Acanthosis Nigricans
The common causes of AN are as follows:
- Diabetes: When the amount of blood glucose rises and the body is unable to use it due to insulin resistance, AN occurs as a sign of high glucose in the body. It also occurs in people who already have type 2 diabetes. 
- Drugs: Some medications like contraceptive pills, thyroid medicines, medications to reduce inflammation (corticosteroids) and also the medicines used to treat the side effects of chemotherapy are known for causing AN. 
- Hormonal changes: Certain medical conditions related to hormonal changes like PCOD  are linked to the cause of AN.
- Race: People belonging to African descent are more prone to this skin condition due to their darker skin. However, it can occur in any individual worldwide due to several medical factors. 
- Hereditary: In some cases, AN is inherited (autosomal dominant), means a child can inherit this skin condition if only one parent has the affected gene. 
- Cancer: The malignant (cancerous) form of AN is commonly linked to cancer of the gastrointestinal tract. Other cancer forms like lymphoma, are also sometimes associated with this velvety skin condition. 
- Obesity: Accumulation of excess of body fat leads to obesity which in turn, leads to diabetes. Thus, obesity is also one of the important factors causing AN. 
Symptoms Of Acanthosis Nigricans
Symptoms of AN are identified by the following:
- Hyperpigmentation or darkening of the skin 
- Roughness or dryness in the affected areas
- Hyperkeratosis or thickening of the skin
- Outgrowth of the skin in the affected area
- Velvety texture on the skin 
- Wrinkled-type on the skin
- Dark-thick patch on one side of the body
In the case of malignant AN, the symptoms are more severe. They are as follows:
- Severe itching or irritation in the affected area
- Shaggy lips 
- Brittle nails
- Wart-like outgrowth around the eyes
- Hair loss
- Thickening of the palm skin 
- Lesions on the mucous membranes like mouth and oesophagus
Risk Factors Of Acanthosis Nigricans
The risk of AN is increased in individuals who
- are overweight, 
- have prediabetic conditions, 
- have a family history of AN and 
- belong to the race whose skin is naturally dark. 
Complications Of Acanthosis Nigricans
As aforementioned, a child with AN is more prone to developing diabetes type 2 in the coming years.
Diagnosis Of Acanthosis Nigricans
The condition is diagnosed through the following methods.
- Complete family and medical history: To get a close view on the patient's race, previous diseases, age and other factors responsible for this skin condition
- Physical examination: By directly looking into the affected area and examining it by the symptoms
- Glucose test: To find the glucose level in the blood 
- Blood and urine tests: To rule out other disorders of the hormones or immune system
- Biopsy: It is done by taking out a small sample of the affected skin and viewing it under a microscope. The test is also done to rule out other skin disorders. 
- X-ray: To determine other underlying causes responsible for the cause of AN
Treatment Of Acanthosis Nigricans
The treatment of AN is usually carried out by treating the condition causing it. In this way, the symptoms can be controlled and the dark-thick patches on the skin totally fade away.
However, one can go for some basic treatment methods mentioned below in case they are concerned about their appearance. They are as follows:
- Skin lightening creams for the affected areas
- Laser therapy for hyperkeratosis 
- Oral acne medications
- Topical antibiotics 
- Antibacterial soaps 
If AN is malignant, medical experts may suggest for surgery, a process in which the tumour is surgically removed to prevent the spread of thick, dark and velvety patches on the skin. It also includes chemotherapy and radiation therapy.
Prevention Of Acanthosis Nigricans
- Lose weight
- Stop taking medications which may seem to cause AN.
- Monitor the blood glucose regularly and keep your diabetes under control.
- If AN is caused due to hormonal imbalance, make some lifestyle changes to stabilize the hormones.
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