 resistance syndromes may be divided into Type A (HAIR-AN) and type B syndromes.:978
Insulin resistance and acanthosis nigricans
In young persons, AN is a visible marker which strongly suggests insulin resistance. Higher than normal insulin levels in the blood stream causes the growth of darkened skin over certain areas of the body. There is no skin treatment that will get rid of AN. Acanthosis Nigricans may lighten up and possibly go away by treating the root cause, Insulin Resistance but it can take months or years to do so.
The majority of cases of acanthosis nigricans are associated with obesity and otherwise idiopathic. This is likely because of insulin resistance, and more likely to occur in darker-skinned persons.:968 This is also known as "Pseudo-Acanthosis Nigricans", or "Type 3 Acanthosis Nigricans".:86
Acral Acanthotic Anomaly
Acral Acanthotic Anomaly refers to a variant of acanthosis nigricans limited to the elbows, knees, knuckles and dorsal surfaces of the feet, in the absence of any other findings, in otherwise healthy individuals. While the etiology remains unknown, its presence does not suggest a likelihood of malignancy.
Malignant acanthosis nigricans refers to acanthosis nigricans occurring as a paraneoplastic syndrome associated with a cancer. Malignant acanthosis nigricans is most-commonly associated with gastrointestinal adenocarcinomas, as well as genitourinary cancers such as those of the prostate, breast, and ovary. Other cancers, such as those of the lung, stomach, and lymphoma, are occasionally associated with acanthosis nigricans.:86
This form of acanthosis nigricans is more likely to involve mucous membranes (25-50% of cases) This variant is also known as Acanthosis nigricans type I:676 or 5.:86 Malignant acanthosis nigricans that may either precede (18%), accompany (60%), or follow (22%) the onset of an internal cancer.:506 Malignancy-associated acanthosis nigricans is usually rapid in onset and may be accompanied by skin tags, multiple seborrheic keratoses, or tripe palms.:676
The pathogenesis of acanthosis nigricans is poorly understood, and likely to relate to an interplay of factors, including insulin-mediated activation of ILGF receptors on keratinocytes, and increased growth factor levels.
Factors involved in the development of acanthosis nigricans include:
- Increased circulating insulin. This activates keratinocyte ILGF receptors, particularly IGF-1. At high concentrations, insulin may also displace IGF-1 from IGFBP. Increased circulating IGF may lead to keratinocyte and dermal fibroblast proliferation.
- Fibroblast growth factor. Hereditary variants are associated with FGFR defects.
- Increased TGF, which appears to be the mechanism for malignancy-associated acanthosis nigricans. TGF acts on epidermal tissue via the EGFR.:86
In conjunction with increased end levels of ILGF, it is likely that perspiration and friction may be necessary predeterminants for lesions.
Acanthosis nigricans is typically diagnosed clinically. 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, or x-rays may be required to eliminate the possibility of diabetes or cancer as the cause.:87
Acanthosis nigricans is likely to improve in circumstances where a known cause is removed. For example, obesity-related acanthosis nigricans will improve with weight loss, and drug-induced acanthosis nigricans is likely to resolve when the drug is ceased. Hereditary variants may or may not fade with age, and malignancy-associated variants may, after a malignancy is removed, fade. :87
People with acanthosis nigricans should be screened for diabetes and, although rare, cancer. Controlling blood glucose levels through exercise and diet often improves symptoms. Topical fade creams (normally used for eliminating age spots) can lighten skin cosmetically in less severe cases. Acanthosis nigricans maligna may resolve if the causative tumor is successfully removed.
|This section requires expansion. (August 2013)|
- "acantho