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Acanthosis nigricans is a brown to black, poorly defined, velvety hyperpigmentation
Hyperpigmentation

In dermatology, hyperpigmentation is the darkening of an area of skin or nail caused by increased melanin....
 of the skin
Skin

The skin is the outer covering of the body, also known as the epidermis. It is the largest organ of the integumentary system made up of multiple layers of epithelial biological tissue, and guards the underlying muscles, bones, ligaments and organ s....
. It is usually found in body folds, such as the posterior and lateral folds of the neck
Neck

The neck is the part of the body on many limbed vertebrates that distinguishes the head from the torso or trunk. The scientific term signifying "of the neck" is nuchal....
, the axilla, groin
Groin

In human anatomy, the groin areas are the two wikt:crease at the junction of the torso with the legs, on either side of the pubic area. A pulled groin muscle usually refers to a pulled Adductor muscles of the hip....
, umbilicus
Navel

The navel is a scar on the abdomen, caused when the umbilical cord is removed from a newborn baby. All Placentalia mammals have a navel. It is fairly conspicuous in humans....
, and other areas.

occurs due to insulin
Insulin

Insulin is a hormone with extensive effects on both metabolism and several other body systems . Insulin causes most of the body's cells to take up glucose from the blood , storing it as glycogen in the liver and muscle, and stops use of fat as an energy source....
 spillover (from excessive production due to obesity or insulin resistance
Insulin resistance

Insulin resistance is the condition in which normal amounts of insulin are inadequate to produce a normal Insulin#Physiological_effects from fat, muscle and liver cell ....
) into the skin which results in its abnormal growth, and the stimulation of color producing cells (melanocytes).

The most common cause would be insulin resistance
Insulin resistance

Insulin resistance is the condition in which normal amounts of insulin are inadequate to produce a normal Insulin#Physiological_effects from fat, muscle and liver cell ....
, usually from type 2 diabetes mellitus
Diabetes mellitus

Diabetes mellitus , often referred to simply as diabetes , is a syndrome of disordered metabolism, usually due to a combination of genetic disorder and environmental causes, resulting in abnormally high blood sugar levels ....
.

Other causes are familial, obesity
Obesity

Obesity is a condition in which excess body fat has accumulated to an extent that health may be negatively affected. It is commonly defined as a body mass index of 30 kg/m2 or higher....
, drug-induced
Medication

A pharmaceutical drug, also referred to as medicine or medicament, can be loosely defined as any substance intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease....
, malignant
Malignant

Malignant is a medical term used to describe a severe and progressively worsening disease. The term is most familiar as a description of cancer....
 (gastric cancer), idiopathic
Idiopathic

Idiopathic is an adjective used primarily in medicine meaning arising spontaneously or from an obscure or unknown cause. From Greek ?d???, idios + p????, pathos , it means approximately "a disease of its own kind."...
, and insulin resistance in Polycystic ovary syndrome
Polycystic ovary syndrome

Polycystic ovary syndrome is an endocrine disorder that affects approximately 5% of all women.It occurs amongst all races and nationalities, is the most common hormonal disorder among women of reproductive age, and is a leading cause of infertility....
.






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Acanthosis nigricans is a brown to black, poorly defined, velvety hyperpigmentation
Hyperpigmentation

In dermatology, hyperpigmentation is the darkening of an area of skin or nail caused by increased melanin....
 of the skin
Skin

The skin is the outer covering of the body, also known as the epidermis. It is the largest organ of the integumentary system made up of multiple layers of epithelial biological tissue, and guards the underlying muscles, bones, ligaments and organ s....
. It is usually found in body folds, such as the posterior and lateral folds of the neck
Neck

The neck is the part of the body on many limbed vertebrates that distinguishes the head from the torso or trunk. The scientific term signifying "of the neck" is nuchal....
, the axilla, groin
Groin

In human anatomy, the groin areas are the two wikt:crease at the junction of the torso with the legs, on either side of the pubic area. A pulled groin muscle usually refers to a pulled Adductor muscles of the hip....
, umbilicus
Navel

The navel is a scar on the abdomen, caused when the umbilical cord is removed from a newborn baby. All Placentalia mammals have a navel. It is fairly conspicuous in humans....
, and other areas.

Causes

This occurs due to insulin
Insulin

Insulin is a hormone with extensive effects on both metabolism and several other body systems . Insulin causes most of the body's cells to take up glucose from the blood , storing it as glycogen in the liver and muscle, and stops use of fat as an energy source....
 spillover (from excessive production due to obesity or insulin resistance
Insulin resistance

Insulin resistance is the condition in which normal amounts of insulin are inadequate to produce a normal Insulin#Physiological_effects from fat, muscle and liver cell ....
) into the skin which results in its abnormal growth, and the stimulation of color producing cells (melanocytes).

The most common cause would be insulin resistance
Insulin resistance

Insulin resistance is the condition in which normal amounts of insulin are inadequate to produce a normal Insulin#Physiological_effects from fat, muscle and liver cell ....
, usually from type 2 diabetes mellitus
Diabetes mellitus

Diabetes mellitus , often referred to simply as diabetes , is a syndrome of disordered metabolism, usually due to a combination of genetic disorder and environmental causes, resulting in abnormally high blood sugar levels ....
.

Other causes are familial, obesity
Obesity

Obesity is a condition in which excess body fat has accumulated to an extent that health may be negatively affected. It is commonly defined as a body mass index of 30 kg/m2 or higher....
, drug-induced
Medication

A pharmaceutical drug, also referred to as medicine or medicament, can be loosely defined as any substance intended for use in the diagnosis, cure, mitigation, treatment, or prevention of disease....
, malignant
Malignant

Malignant is a medical term used to describe a severe and progressively worsening disease. The term is most familiar as a description of cancer....
 (gastric cancer), idiopathic
Idiopathic

Idiopathic is an adjective used primarily in medicine meaning arising spontaneously or from an obscure or unknown cause. From Greek ?d???, idios + p????, pathos , it means approximately "a disease of its own kind."...
, and insulin resistance in Polycystic ovary syndrome
Polycystic ovary syndrome

Polycystic ovary syndrome is an endocrine disorder that affects approximately 5% of all women.It occurs amongst all races and nationalities, is the most common hormonal disorder among women of reproductive age, and is a leading cause of infertility....
. In the context of a malignant disease, Acanthosis nigricans is a paraneoplastic syndrome and is then commonly referred to as Acanthosis nigricans maligna. Involvement of mucous membranes is rare and suggests a coexisting malignant condition. It typically occurs in individuals younger than age 40, may be genetically inherited, and is associated with obesity or endocrinopathies, such as hypothyroidism or hyperthyroidism, acromegaly, polycystic ovary disease, insulin-resistant diabetes, or Cushing's disease. When seen in individuals older than age 40, this disorder is commonly associated with an internal malignancy, usually adenocarcinoma, and most commonly of the GI tract or uterus; less commonly of the lung, prostate, breast, or ovary. Acanthosis nigricans of the oral mucosa or tongue is highly suggestive of a neoplasm, especially of the GI tract.[2]

Types

Acanthosis nigricans may be divided into the following types:
  • Acanthosis nigricans type I
  • Acanthosis nigricans type II
  • Acanthosis nigricans type III


Signs and tests

Physicians can usually diagnose acanthosis nigricans by simply looking at a patient's skin. A skin biopsy may be needed in unusual cases. If no clear cause of acanthosis nigricans is obvious, it may be necessary to search for one. Blood tests, an endoscopy
Endoscopy

Endoscopy means looking inside and typically refers to looking inside the body for medical reasons using an instrument called an endoscope....
, or x-ray
X-ray

X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 10 to 0.01 nanometers, corresponding to frequency in the range 30 Hertz to 30 Hertz and energies in the range 120 Electron volt to 120 keV....
s may be required to eliminate the possibility of diabetes or cancer
Cancer

Cancer is a class of diseases in which a group of cell display uncontrolled growth , invasion , and sometimes metastasis . These three malignant properties of cancers differentiate them from benign tumors, which are self-limited, do not invade or metastasize....
 as the cause.

Treatment

People with acanthosis nigricans should be screened for diabetes
Diabetes mellitus

Diabetes mellitus , often referred to simply as diabetes , is a syndrome of disordered metabolism, usually due to a combination of genetic disorder and environmental causes, resulting in abnormally high blood sugar levels ....
 and, although rare, cancer
Cancer

Cancer is a class of diseases in which a group of cell display uncontrolled growth , invasion , and sometimes metastasis . These three malignant properties of cancers differentiate them from benign tumors, which are self-limited, do not invade or metastasize....
. Controlling blood glucose levels through exercise and diet often improves symptoms.

Prognosis

Acanthosis nigricans often fades if the underlying cause can be determined and treated appropriately.

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