الفهرس 
Aetiology of striae distensaeOnly 14 pages are availabe for public view
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Abstract
Striae distensae (stretch marks) are a common disfiguring condition associated with continuous and progressive stretching of the skin.
The aetiology of the striae are poorly understo- od, striae may develop as a result of stress rupture of the connective tissue framework or develope as a result of many other causes.
Genetic factors play an important role in the development of striae, the procollagen and fibronectin gene expression is markedly decreased in striae distensae, also there is a decrease in (I) and (III) procollagen mRNA levels in SD compared with normal tissue.
Continuous stretching also plays a role in development striae. Striae develop as a result of continuous stretching usually parallel to the resting tension lines.
Both systemic and local glucocorticoid therapy can produce cutaneous atrophy by a dose related pharmacological effect. The mode of action of corticosteroids is through inhibition of collagen gene expression which occurs at transcriptional, translational and post-translational level.
Steroids also known to inhibit the formation of glycosaminoglycans.
Oral contraceptive pills and hormonal effects in pregnancy play a role in developing SD. Oral contraceptive pills increase cortisol level in blood which leads to the development of SD. In pregnancy hormonal effect and stretch factor, both lead to the appearance of SD.
In the past, SD were observed with many debilitating conditions such as tuberculosis, typhoid fever, also in Marfan syndrome and diabetes mellitus. In nutritionally deprivated states, there is an increased risk of deficiency of ascorbic acid essential for normal collagen synthesis as a required co-factor for hydroxyl-
ation of proline and lysine, however, the basic aetiology is not known.
Clinically striae pass through distinct stages; initially they appear as raised pink purple linear lesions without significant depression of the skin (rubra) ,but with time they maturate to become paler, depressed and finally wrinkled (alba) .
Striae usually appear in the lower back,abdomen, upper arm and legs. Usually striae are a cosmetic
Problem, they can be prevented by limiting weight
gain, gets lot of exercise and take plenty of fluids.
By light microscopy, early lesions shows superficial and deep perivascular infiltrate of lymphocyte and esinophils. Elastic fibers in early lesion appear in the periphery thick and tortuous, but the older lesions show normal appearance of elastic fibers.
By scanning electron microscopy, there are extensive tangles of fine curled elastic fibers with a random arrangement. Bundles of collagen are thinned and aligned parallel to the skin surface .In the late stage ,these finding are exaggerated with a thin epidermis devoid of rete ridges .
Different methods have been used in the treatment of striae distensae which include; peeling agent like tricholoracetic acid ,glycolic acid, microdermabrasion, topical tretinoin and many types of laser.
Topical tretinoin increases the deposition of collagen and increases the presence of fibroblasts in the area of its application. In a concentration of 0.05% and 1% is found to be effective in treatment of early stretch marks but with no significant effect in mature stretch marks.
Trichloroacetic acid in low concentration 15-20% with repeated application at monthly interval produces significant improvement according to the skin texture.
Microdermabrasion is one of the most widely used methods in the world leads to improvement after 6 to10 sessions. Microdermabrasion when combined with topical agent containing glycolic acid, topical retinoids may produce better clinical results than microdermabrasion alone.
Differernt types of laser have been used in the treatment of striae which include; Flashlamp pumped pulsed dye laser (PDL; 585nm) which is the most commonly reported laser for the treatment of stria. It produces clinical improvement for 6 to 12 months after laser irradiation . Fluence of 3 J/cm seemed to be optimal , to improve striae appearance. However, pulsed dye laser may not be a suitable treatment option for patients with darker skin , so caution should be used on darker skin types.
Short pulsed carbon dioxide lasers produces unsatisfactory results in treatment of striae , it should be used with a great caution in types I, II, and III, and should be avoided in skin types IV,V and VI.
Erbium: Yttrium-aluminum-garnet is effective in improving striae. Since it produces little thermal damage, side effects as pigmentary changes and scarring are rare .
Intense pulsed light seems to be a promising alternative for the treatment of the striae distensae as it found to have a clinical benefit and less side effects. It can be used in the treatment of both types of striae .
Lastly, cosmetic surgery may be used as a last resort for the most severe scarring form of stretch marks.