出典(authority):フリー百科事典『ウィキペディア（Wikipedia）』「2016/01/06 14:57:00」(JST)
| Stretch marks | |
|---|---|
| Classification and external resources | |
| Specialty | Dermatology |
| ICD-10 | L90.6 |
| ICD-9-CM | 701.3 |
| DiseasesDB | 30027 |
| MedlinePlus | 003287 |
| eMedicine | derm/406 |
Stretch marks or striae (singular stria) or striae distensae, as they are called in dermatology, are a form of scarring on the skin with an off-color hue. They are caused by tearing of the dermis, which over time may diminish, but will not disappear completely.
Stretch marks are often the result of the rapid stretching of the skin associated with rapid growth or rapid weight changes. Stretch marks in most cases may also be influenced by hormonal changes associated with puberty, pregnancy, bodybuilding, hormone replacement therapy, etc.[1] Medical terminology for these kinds of markings includes striae atrophicae, vergetures, stria distensae, striae cutis distensae, lineae atrophicae, linea albicante, or simply striae. Stretch marks formed during pregnancy, usually during the last trimester, and usually on the belly, but also commonly occurring on the breasts, thighs, hips, lower back and buttocks, are known as striae gravidarum.[2]
Striae, or "stretch marks", begin as reddish or purple lesions, which can appear anywhere on the body, but are most likely to appear in places where larger amounts of fat are stored; the most common places are the abdomen (especially near the navel), breasts, upper arms, underarms, back, thighs (both inner and outer), hips, and buttocks. Over time, they tend to atrophy and lose pigmentation. The affected areas appear empty, and are soft to the touch.[3]
Stretch marks occur in the dermis, the resilient middle tissue layer that helps the skin retain its shape. No stretch marks will form as long as there is support within the dermis; stretching plays a role in where the marks occur and in what direction they run, however, there are a number of contributing factors (see: "Causes", below) to their formation. They can (but do not always) cause a burning and itching sensation, as well as emotional distress. They pose no health risk in and of themselves, and do not compromise the body's ability to function normally and repair itself,[4] however, they are often considered a cosmetic nuisance.[5] Young women are generally affected the most and often seek treatment for them from a dermatologist[6] and following pregnancy.[7]
The Mayo Clinic states that "[s]tretch marks seem to be caused, literally, by a stretching of the skin," and adds: "Stretch marks are more extreme when coupled with an increase in cortisone, a hormone produced by the adrenal glands. Cortisone weakens elastic fibers in the skin."[8]
In other words, an increase in cortisone levels can increase the probability or severity of stretch marks by reducing the skin's pliability; more specifically, it affects the dermis by preventing the fibroblasts from forming collagen and elastin fibers, necessary to keep rapidly growing skin taut. This can create a lack of supportive material as the skin is stretched, and lead to dermal and epidermal tearing, which in turn can produce scarring in the form of stretch marks. This is particularly the case when there is new tissue growth (which can interfere with the underlying physical support of the dermis or epidermis, by displacing the supportive tissue).
Examples of cases where stretch marks are common, also given by the Mayo Clinic, include weight gain (in the form of fat and/or muscle), pregnancy, and adolescent growth spurts, though it is also noted that some medications, as well as other medical conditions and diseases, may increase the likelihood of stretch marks appearing. In the case of medication, the Clinic points to "Corticosteroid creams, lotions and pills and chronic use of oral or systemic steroids" as a common contributing factor; in the case of medical conditions that can contribute to stretch marks, examples given include Ehlers-Danlos syndrome, Cushing's syndrome, Marfan syndrome, and "adrenal gland diseases".
A number of additional factors appear to promote the appearance of stretchmarks: one study of 324 women, done just after they had given birth, demonstrated that low maternal age, high body mass index, weight gain over 15 kg (33 pounds) and higher neonatal birth weight were independently correlated with the occurrence of striae. Teenagers were found to be at the highest risk of developing severe striae.[9]
Striae gravidarum or pregnancy stretch marks, is a specific form of scarring of the skin of the abdominal due to sudden weight gain during pregnancy. These off-color blemishes are symptoms of pregnancy caused by the tearing of the dermis, resulting in atrophy and loss of rete ridges.[10] These scars often appear as reddish or bluish streaks on the abdomen, and can also appear on the breasts and thighs. Some of these striae disappear with time, while others remain as permanent discolorations of the body.[5]
Mechanical distention and rapidly developing areas of the body during pregnancy (such as the abdomen, breasts, and thighs) are most commonly associated with striae formation. Some have suggested that relaxin and estrogen combined with higher levels of cortisol during pregnancy can cause an accumulation of muocopolysaccharides, which increases water absorption of connective tissue, making it prime for cleavage under mechanical stress.[6][9] There also seems to be an association between higher body mass indices and in women with bigger babies and the incidence and severity of striae. Also, younger women seem to be at higher risk of developing striae during pregnancy.[6][11]
The prevalence and severity of striae gravidarum varies among populations. The current literature suggest that in the general population of the US, there is a 50%-90% prevalence of striae associated with pregnancy,[11] partly as a result of the normal hormonal changes of pregnancy and partly due to stretching of skin fibers.[12][13] Many women experience striae gravidarum during their first pregnancy. Nearly 45% percent of women develop striae gravidarum before 24 weeks of gestation.[5] Interestingly, many women who develop lesions during the first pregnancy do not develop them during later pregnancies. Genetic factors such as family history and race also seem to be predictive in the appearance of striae.[14]
A systematic review has not found evidence that the creams and oils that have been studied for preventing or reducing stretch marks in pregnancy are effective.[12] The safety in pregnancy of one ingredient, Centella asiatica, has been questioned.[13] Evidence on treatments for reducing the appearance of the scars after pregnancy is limited.[13]
Since ancient times, pregnant women have sought remedies to prevent stretch marks during pregnancy. Both ancient Greeks and Romans used olive oil, while Ethiopians and Somalians used frankincense.[15] Both of these treatments have surged in their use in recent years. Results of modern studies have offered conflicting results regarding the efficacy of various topical ointments. Conventional treatment includes topical 0.1% tretinoin (all-trans-retinoic acid) cream mixed with various lotions and moisturizers. Some unconventional prevention therapies include applying castor oil, taking thiosinaminum, applying seaweed wraps, using topical glycolic or fruit acids, and various other homeopathic creams and/or oils.[16] To date, nothing appears to definitively prevent striae gravidarum from forming.[11]
Various treatments are available for the purpose of improving the appearance of existing stretch marks, including laser treatments, dermabrasion, and prescription retinoids.[citation needed] Topical tretinoin (prescription retinoid) is categorized by the FDA as a known teratogen (causing malformations in fetuses) in animals, without adequate human studies on safety in pregnancy.[17] Some cream manufacturers claim the best results are achieved on recent stretch marks; however, few studies exist to support these claims.
Some success has been made in treating and eliminating striae gravidarum. Some studies have examined the use of 20% glycolic acid and 10% L-ascorbic acid with zinc sulfate and tyrosine, as well as laser treatments in reducing the appearance of striae.[16][18]
A surgical procedure for removing lower abdominal stretch marks is the tummy tuck, which removes the skin below the navel where stretch marks frequently occur.
A new modality, fractional laser resurfacing, offers a novel approach to treating striae.[19] Using scattered pulses of light only a fraction of the scar is zapped by the laser over the course of several treatments. This creates microscopic wounds. The body responds to each treatment by producing new collagen and epithelium. In a 2007 clinical trial, 5-6 treatments resulted in striae improving by as much as 75 percent.[20] A 2007 Brazilian clinical study showed that fractional laser resurfacing improved both texture and appearance of mature, white striae in skin types I-IV.[21]
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| リンク元 | 「皮膚線条」「脈理」 |
| 拡張検索 | 「Baillarger's striae」 |