Acanthosis nigricans
Encyclopedia
Acanthosis nigricans is a brown to black, poorly defined, velvety hyperpigmentation
of the skin
. It is usually found in body folds, such as the posterior and lateral folds of the neck
, the axilla, groin
, umbilicus
, forehead
, and other areas.
or hyperthyroidism
, acromegaly
, polycystic ovary disease, insulin-resistant diabetes, or Cushing's disease
.
, which leads to increased circulating insulin levels. Insulin
spillover into the skin results in its abnormal increase in growth (hyperplasia of the skin). The condition most commonly associated with insulin resistance is type 2 diabetes mellitus
, but is also a prominent feature of obesity
, polycystic ovary syndrome
, Donohue syndrome
, and Rabson-Mendenhall syndrome
. Acanthosis nigricans may also be seen with certain medications that lead to elevated insulin levels (e.g., glucocorticoids, niacin, insulin, oral contraceptives, and protease inhibitors).
and is then commonly referred to as acanthosis nigricans maligna. Involvement of mucous membranes is rare and suggests a coexisting malignant condition.
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. The stomach is the most common site. Acanthosis nigricans of the oral mucosa or tongue is highly suggestive of a neoplasm, especially of the GI tract.
and idiopathic
.
Classification of Acanthosis nigricans according to Schwartz
, or x-ray
s may be required to eliminate the possibility of diabetes or cancer
as the cause.
Additionally acanthosis nigricans has similar visual characteristics (neck discoloration) with Casal collar
, which is a symptom of pellegra (a nutrient deficiency disease, easily remedied with supplementation). In early stages of discoloration, it is hard for a non trained eye to distinguish one from the other.
and, although rare, cancer
. Controlling blood glucose levels through exercise and diet often improves symptoms. Acanthosis nigricans maligna may resolve if the causative tumor is successfully removed.
Hyperpigmentation
In dermatology, hyperpigmentation is the darkening of an area of skin or nails caused by increased melanin.-Causes:Hyperpigmentation may be caused by sun damage, inflammation, or other skin injuries, including those related to acne vulgaris...
of the skin
Skin
-Dermis:The dermis is the layer of skin beneath the epidermis that consists of connective tissue and cushions the body from stress and strain. The dermis is tightly connected to the epidermis by a basement membrane. It also harbors many Mechanoreceptors that provide the sense of touch and heat...
. 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 terrestrial or secondarily aquatic vertebrates, that distinguishes the head from the torso or trunk. The adjective signifying "of the neck" is cervical .-Boner anatomy: The cervical spine:The cervical portion of the human spine comprises seven boney...
, the axilla, groin
Groin
In human anatomy, the groin areas are the two creases at the junction of the torso with the legs, on either side of the pubic area. This is also known as the medial compartment of the thigh. A pulled groin muscle usually refers to a painful injury sustained by straining the hip adductor muscles...
, umbilicus
Navel
The navel is a scar on the abdomen caused when the umbilical cord is removed from a newborn baby...
, forehead
Zebibah
A zebibah is a darkened area of callused skin on the forehead. Muslims sometimes acquire one from pressing the head to the ground during daily prayers...
, and other areas.
Causes
It typically occurs in individuals younger than age 40, may be genetically inherited, and is associated with obesity or endocrinopathies, such as hypothyroidismHypothyroidism
Hypothyroidism is a condition in which the thyroid gland does not make enough thyroid hormone.Iodine deficiency is the most common cause of hypothyroidism worldwide but it can be caused by other causes such as several conditions of the thyroid gland or, less commonly, the pituitary gland or...
or hyperthyroidism
Hyperthyroidism
Hyperthyroidism is the term for overactive tissue within the thyroid gland causing an overproduction of thyroid hormones . Hyperthyroidism is thus a cause of thyrotoxicosis, the clinical condition of increased thyroid hormones in the blood. Hyperthyroidism and thyrotoxicosis are not synonymous...
, acromegaly
Acromegaly
Acromegaly is a syndrome that results when the anterior pituitary gland produces excess growth hormone after epiphyseal plate closure at puberty...
, polycystic ovary disease, insulin-resistant diabetes, or Cushing's disease
Cushing's disease
Cushing's disease is a cause of Cushing's Syndrome characterised by increased secretion of adrenocorticotropic hormone from the anterior pituitary. This is most often as a result of a pituitary adenoma...
.
Endocrine
The most common cause of acanthosis nigricans is insulin resistanceInsulin resistance
Insulin resistance is a physiological condition where the natural hormone insulin becomes less effective at lowering blood sugars. The resulting increase in blood glucose may raise levels outside the normal range and cause adverse health effects, depending on dietary conditions. Certain cell types...
, which leads to increased circulating insulin levels. Insulin
Insulin
Insulin is a hormone central to regulating carbohydrate and fat metabolism in the body. Insulin causes cells in the liver, muscle, and fat tissue to take up glucose from the blood, storing it as glycogen in the liver and muscle....
spillover into the skin results in its abnormal increase in growth (hyperplasia of the skin). The condition most commonly associated with insulin resistance is type 2 diabetes mellitus
Diabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
, but is also a prominent feature of obesity
Obesity
Obesity is a medical condition in which excess body fat has accumulated to the extent that it may have an adverse effect on health, leading to reduced life expectancy and/or increased health problems...
, polycystic ovary syndrome
Polycystic ovary syndrome
Polycystic ovary syndrome is one of the most common female endocrine disorders. PCOS is a complex, heterogeneous disorder of uncertain aetiology, but there is strong evidence that it can to a large degree be classified as a genetic disease....
, Donohue syndrome
Donohue syndrome
Donohue syndrome is an extremely rare and severe genetic disorder. Leprechaunism derives its name from the fact that those afflicted with the disease often have elfin features and are smaller than usual...
, and Rabson-Mendenhall syndrome
Rabson-Mendenhall syndrome
Rabson–Mendenhall syndrome is a rare insulin receptor disorder characterized by severe insulin resistance, developmental abnormalities, and acanthosis nigricans...
. Acanthosis nigricans may also be seen with certain medications that lead to elevated insulin levels (e.g., glucocorticoids, niacin, insulin, oral contraceptives, and protease inhibitors).
Malignant
In the context of a malignant disease, acanthosis nigricans is a paraneoplastic syndromeParaneoplastic syndrome
A paraneoplastic syndrome is a disease or symptom that is the consequence of the presence of cancer in the body, but is not due to the local presence of cancer cells. These phenomena are mediated by humoral factors excreted by tumor cells or by an immune response against the tumor...
and is then commonly referred to as acanthosis nigricans maligna. Involvement of mucous membranes is rare and suggests a coexisting malignant condition.
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. The stomach is the most common site. Acanthosis nigricans of the oral mucosa or tongue is highly suggestive of a neoplasm, especially of the GI tract.
Other
Other causes of acanthosis nigricans are familial, drug-inducedMedication
A pharmaceutical drug, also referred to as medicine, medication or medicament, can be loosely defined as any chemical substance intended for use in the medical diagnosis, cure, treatment, or prevention of disease.- Classification :...
and idiopathic
Idiopathic
Idiopathic is an adjective used primarily in medicine meaning arising spontaneously or from an obscure or unknown cause. From Greek ἴδιος, idios + πάθος, pathos , it means approximately "a disease of its own kind". It is technically a term from nosology, the classification of disease...
.
Classification of Acanthosis nigricans according to SchwartzRobert A. SchwartzRobert A. Schwartz is an American physician and the discoverer of the Schwartz-Burgess Syndrome. He is a professor and the Head of the Department of Dermatology at New Jersey Medical School...
, 1994
- Benign acanthosis nigricans
- Acanthosis nigricans associated with obesity
- Syndromic acanthosis nigricans
- Malignant acanthosis nigricans
- Acral acanthosis nigricans
- Unilateral acanthosis nigricans
- Drug-induced acanthosis nigricans
- Mixed acanthosis nigricans
Other Classifications of Acanthosis nigricans
Acanthosis nigricans may also be divided into the following types:- Acral Acanthotic Anomaly (Acral Acanthosis Nigricans)
- Acanthosis nigricans type I
- Acanthosis nigricans type II
- Acanthosis nigricans type III
Signs, tests, and misdiagnoses
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 endoscopyEndoscopy
Endoscopy means looking inside and typically refers to looking inside the body for medical reasons using an endoscope , an instrument used to examine the interior of a hollow organ or cavity of the body. Unlike most other medical imaging devices, endoscopes are inserted directly into the organ...
, or x-ray
X-ray
X-radiation is a form of electromagnetic radiation. X-rays have a wavelength in the range of 0.01 to 10 nanometers, corresponding to frequencies in the range 30 petahertz to 30 exahertz and energies in the range 120 eV to 120 keV. They are shorter in wavelength than UV rays and longer than gamma...
s may be required to eliminate the possibility of diabetes or cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
as the cause.
Additionally acanthosis nigricans has similar visual characteristics (neck discoloration) with Casal collar
Casal collar
The Casal collar or Casal necklace is a clinical sign in which there is erythematous pigmented skin rash in the distribution of a broad collar . It is seen in patients with pellagra.The sign is named after Gaspar Casal....
, which is a symptom of pellegra (a nutrient deficiency disease, easily remedied with supplementation). In early stages of discoloration, it is hard for a non trained eye to distinguish one from the other.
Treatment
People with acanthosis nigricans should be screened for diabetesDiabetes mellitus
Diabetes mellitus, often simply referred to as diabetes, is a group of metabolic diseases in which a person has high blood sugar, either because the body does not produce enough insulin, or because cells do not respond to the insulin that is produced...
and, although rare, cancer
Cancer
Cancer , known medically as a malignant neoplasm, is a large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body. The cancer may also spread to more distant parts of the...
. Controlling blood glucose levels through exercise and diet often improves symptoms. Acanthosis nigricans maligna may resolve if the causative tumor is successfully removed.
Prognosis
Acanthosis nigricans often fades if the underlying cause can be determined and treated appropriately.External links
- http://www.mayoclinic.com/print/acanthosis-nigricans/DS00653/DSECTION=all&METHOD=print
- AOCD
- http://www.skinsight.com/adult/acanthosisNigricans-references.htm