What is acanthosis nigricans?
Acanthosis nigricans (AN) is a disease condition where there are areas of dark and smoothly thickened (velvety) areas of the skin. These may due to unusually increased skin pigmentation (hyperpigmentation) and an increase in the number of skin cells (hyperkeratosis). Acanthosis nigricans is a skin condition on its own but more significantly may be the consequence of certain metabolic disturbances in the body. It therefore extends beyond just a cosmetic concern.
What causes acanthosis nigricans?
The underlying causes for development of acanthosis nigricans is not well known. It is more frequently seen with hormone disturbances and other metablic disorders. Factors that cause abnormal increase in number of skin cells play an important role in development of acanthosis nigricans. Some of the conditions where acanthosis nigricans is seen includes :
- Type-2 diabetes-associated acanthosis nigricans . This is among the more common instances. Patients with acanthosis nigricans are associated with resistance to insulin (a hormone that regulates the glucose levels in the body and secreted by pancreas) and develop type-2 diabetes eventually.
- Obesity-associated acanthosis nigricans. Here patients who develop acanthosis nigricans have excess accumulation of body fat and are obese or overweight. They also have high chances of developing insulin resistance and eventually diabetes mellitus.
- Hormonal disorder-associated acanthosis nigricans. It is also known as syndromic acanthosis nigricans as it is associated with syndromes or disorders (polycystic ovaries, underactive thyroid gland or overactive adrenal glands).
- Drug-induced acanthosis nigricans. This is not common. It is caused by taking various medications (nicotinic acid, insulin, oral contraceptives and corticosteroids like prednisone).
- Cancer-associated acanthosis nigricans, also known as malignant acanthosis nigricans, develops gradually with cancerous tumors of the internal organs (stomach, colon or liver).
What are the symptoms of acanthosis nigricans?
Areas with more skin folds (neck, groin and armpits) are more likely to develop acanthosis nigricans. Sometimes it is seen on the lips, palms and soles of the feet.
- Changes in skin texture and colour are the only symptoms or signs associated with severe acanthosis nigricans.
- The skin changes like darkening, smoothening and thickening of skin folds appear gradually over months or years.
- There is usually no itching, pain or other abnormal sensation on the affected area.
What is the treatment for acanthosis nigricans?
Acanthosis nigricans is diagnosed by physical inspection coupled with the medical history and presence of other conditions. A skin biopsy may reveal thickening of the skin. Acanthosis nigricans treatment is primarily directed at reducing the symptoms. Treatment preference does not exist specifically for acanthosis nigricans, but involves treating and managing the underlying disease process.
Ideally acanthosis nigricans should be avoided by properly treating, managing and preventing the causative conditions in the following ways :
- In case of obesity-associated acanthosis nigricans losing weight may help reduce symptoms.
- With drug-induced acanthosis nigricans discontinuation of medicines will help resolve symptoms.
- For cancer-associated acanthosis nigricans surgical removal of the tumor generally reduce the symptoms of skin darkening.
The other effective treatments can be application of topical medication.
- Keratolytics (0.05 % topical tretinoin and/or 12 % ammonium lactate cream)
- Depigmentation creams (0.05 % topical tretinoin, 4 % hydroquinone and 0.01 % fluocinolone acetonide)
- Calcipotriol, podophyllin, urea, and salicylic
Laser therapy to reduce thickness of skin folds may be helpful for palliative care. Other abrasive therapies should be avoided as it can worsen the condition.