Stretch marks
Synonyms and keywords: Striae, striae atrophicae.

# Overview
Stretch marks or striae, as they are called in dermatology, are a form of scarring on the skin with a silvery white hue. They are caused by tearing of the dermis, and over time can diminish but not disappear completely.  Stretch marks are the result of the rapid stretching of the skin associated with rapid growth (common in puberty) or weight gain (e.g. pregnancy). Although the skin is fairly elastic, rapid stretching of the skin will leave permanent stretch marks. (Source: WD Writers). Stretch marks are generally associated with pregnancy, obesity, and can develop during rapid muscle growth from steroid use.  Stretch marks are also referred to as striae distensae. Medical terminology for these kinds of markings include striae atrophicae, vergetures, striae cutis distensae, striae gravidarum (in cases where it is caused by pregnancy), lineae atrophicae, striae distensae, linea albicante, or simply striae.

# Symptoms and signs
They first appear as reddish or purple lines, but tend to gradually fade to a lighter color. The affected areas appear empty and soft to the touch.
Human skin has three different layers: the epidermis (outer layer), the dermis (middle layer), and the subcutaneous stratum (innermost layer). Stretch marks occur in the dermis, the resilient middle layer that helps the skin retain its shape.
No stretch marks will form as long as there is support within the dermis. Stretching plays more of a role in where the marks occur and in what direction they run. Stretching alone is not the cause.
Stretch marks can appear anywhere on the body, but are most likely to appear in places where larger amounts of fat are stored. Most common places are the abdomen (especially near the belly-button), breasts, upper arms, underarms, thighs (both inner and outer), hips, and buttocks. They pose no health risk in and of themselves, and do not compromise the body's ability to function normally and repair itself.

# Causes
The glucocorticoid hormones responsible for the development of stretch marks affect the epidermis by preventing the fibroblasts from forming collagen and elastin fibers, necessary to keep rapidly growing skin taut. This creates a lack of supportive material, as the skin is stretched and leads to dermal and epidermal tearing. If the epidermis and the dermis has been penetrated, laser will not remove the stretch marks.

# Physical examination

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# Prevention and cure
Between 75% and 90% of women develop stretch marks to some degree during pregnancy. The sustained hormonal levels as a result of pregnancy usually means stretch marks may appear during the sixth or seventh month.
Only one randomised controlled study has been published which claimed to test whether oils or creams prevent the development of stretchmarks. This study found a daily application of a cream (Trofolastin) containing Centella asiatica extract, vitamin E, and collagen-elastin hydrolysates was associated with fewer stretch marks during pregnancy. Another study, though lacking a placebo control, examined a cream (Verum) containing vitamin E, panthenol, hyaluronic acid, elastin and menthol. It was associated with fewer stretch marks during pregnancy versus no treatment.
Though cocoa butter is an effective moisturizer, no research studies have shown its ability to either prevent stretchmarks, or improve their appearance once a stretchmark has already formed.
Various treatments are available for the purpose of improving the appearance of existing stretch marks, including laser treatments, dermabrasion, and prescription retinoids. Used daily for one month, they resulted in significant improvement in the appearance of a stretchmark's length, depth, and irregular surface area. Some cream manufacturers claim the best results are achieved on recent stretch marks; however, few studies exist to support these claims.
A recent study in the journal "Dermatologic Surgery" has shown that radiofrequency combined with 585-nm pulsed dye laser treatment gave "good and very good" subjective improvement in stretch marks in 89.2% of 37 patients, although further studies will be required to follow up on these results.  In addition, the use of a pulsed dye laser has shown to increase pigmentation in darker skinned individuals with repeated treatments.
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. 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 and as such is a  "no downtime" procedure. The body responds to each treatment by producing new collagen and epithelium. In a 2007 clinical trial, 5-6 treatments has resulted in striae improving by as much as 75 percent. A 2007 Brazilian clinical study has shown Fraxel to improve both texture and appearance of mature, white striae in skin types I-IV: "Fractional Photothermolysis for the treatment of Striae Distensae" Otavio Macedo, Consultorio Clinico Dr. Otavio Macedo Ltda, Brazil, 2007.