There are many different skin conditions that can cause hyperpigmentation – this means darkening of the skin. However, one such condition that is not well known is acanthosis nigricans. It can affect any age group but it is important to note in seniors who often have some of the conditions that are likely causes of the skin discoloration.

Acanthosis nigricans is a brown to black, velvety, darkening of skin folds and creases, sometimes accompanied by a bad smell. It usually affects the skins of armpit, groin, neck, umbilicus (navel) and/or forehead. This skin disorder tends to affect obese people or diabetics. Very rarely it can occur in patients with stomach, liver, lung or ovarian cancer.

Symptoms of acanthosis nigricans

In acanthosis nigricans the only affected organ is the skin.

• Darkening and thickening of body folds and creases which is slowly progressing (often over months to years).
• Usually the armpit, groin and neck is affected.
• Sometimes lips, palm and soles can be affected.
• Bad smell or itching can be present at the site of the darkening.

Symptoms of the underlying disease usually diabetes can also be present but this is no due to acanthosis nigricans.

Causes and risk factors

Acanthosis nigricans usually affects people younger than 40 years. However, it can in some instances start up later in life particularly when associated with cancer and the use of certain drugs. The various causes and risk factors include :

• Obesity (BMI>30)
• Ethnicity – certain ethnic groups are at a greater risk
• Hormonal imbalance: Hypothyroidism or hyperthyroidism, Cushing’s disease, polycystic ovarian disease and especially type 2 diabetes mellitus.
• Drug induced: Glucocorticoids(prednisolone), oral contraceptive pills, niacin, growth hormones (mainly drugs that raise insulin level in the body) can cause acanthosis nigricans in the recipient.
• Hereditary: can affect members of the same family.
• Cancer: Sometimes it can be associated with stomach, liver, lymph nodes (lymphoma). Involvement of oral mucous membrane and tongue with acanthosis nigricans is highly suggestive of gastrointestinal cancer most commonly stomach, but lungs, uterus, breast, ovary or prostate cancer can also coexist ( known as acanthosis nigricans maligna). Acanthosis in older persons (>40yrs) is often associated with cancer.
• Idiopathic: no specific cause can be attributed.

Treatment

Acanthosis nigricans itself is not a disease but is a clinical sign indicative of conditions like type 2 diabetes, cancer, hormonal imbalance and so on. As such there is no specific treatment for the condition. The following measures may be of some use in easing the severity of the condition depending on the underlying causes.

• Exercise and blood sugar control in patients of type 2 diabetes mellitus.
• Weight control.
• Acanthosis co-exists with malignancy (cancer) and sometimes heals after surgical removal of the tumor.
• Other drug treatment to correct hyper or hypothyroidism, polycystic ovarian disease, Cushing’s disease sometimes improves the condition.

More specific measures for treating darkening of the skin, thickened patches, and other symptoms associated with acanthosis nigricans includes :

• Skin lightening cream
• Oral or topicalantibiotics
• Oral antihistaminics (to reduce itching)
• Laser therapy can be used to reduce the thickening and darkening (hyperpigmentation) of the skin.

Acanthosis nigricans often heals if the co-existing underlying cause can be treated successfully.