Acanthosis nigricans (ah-kan-THO-sis NY-gruh-kans) is a skin condition. It
causes thicker and darker patches or streaks around joints and body areas with many
creases and folds (such as knuckles, armpits, elbows, knees, and the sides and back
of the neck).
Some people also develop acanthosis nigricans on their palms, groin, lips, or,
in very rare cases, non-crease areas like the face, back, arms, or legs. The skin
may stay soft, which is why the word "velvety" is often used to describe the symptoms
of acanthosis nigricans.
Acanthosis nigricans is not an infection and isn't contagious. A few kids might
have mild itching, but otherwise acanthosis nigricans is harmless. Still, a doctor
will run tests to rule out underlying causes that could require treatment.
Managing acanthosis nigricans means treating the conditions that are causing the
skin darkening.
Causes
Acanthosis nigricans is most commonly found in children
with high blood insulin levels, a condition often associated with kids who are overweight or
obese or have diabetes.
Sometimes acanthosis nigricans can be a warning sign of other more serious conditions,
such as certain cancers and endocrine problems, along with type 2 diabetes and the
health issues associated with obesity.
In rare cases, acanthosis nigricans can be caused by certain medicines, such as
oral contraceptives
and cholesterol medicine. In some cases, it can be hereditary (passed on to a
person by his or her parents).
Symptoms
Usually, the only signs of acanthosis nigricans will be dark, thick, velvety
patches of skin in creases and folds, usually in the neck, armpits, or groin. But
it's sometimes found in the lips, palms, knuckles, soles of the feet, and other areas.
In rare cases, children may have mild itching in the affected areas.

The patches of skin will usually change color slowly,
over the course of months or even years. If your child's skin changes color rapidly,
call your doctor right away. It could be a sign of a serious medical condition.