<unk>  appear to be caused by<unk> ing of the skin. This is especially true when there is an increase in cortisone an increase in cortisone levels can increase the probability or severity of<unk>  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<unk> ed, and lead to dermal and epidermal tearing, which in turn can produce scarring in the form of<unk> . 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<unk>  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<unk>  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. Medical conditions that can contribute to<unk>  include Ehlers-Danlos syndrome, Cushing's syndrome, Marfan syndrome, and "adrenal gland diseases". Pregnancy Pregnancy<unk> , also known as striae gravidarum, are a specific form of scarring of the skin of the abdominal area due to rapid expansion of the uterus as well as sudden weight gain during pregnancy. About 90% of pregnant women are affected. A number of additional factors appear to promote the appearance of<unk> : 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. These skin<unk>  are symptoms of pregnancy caused by the tearing of the dermis, resulting in atrophy and loss of rete ridges. 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. Mechanical distension 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 mucopolysaccharides, which increases water absorption of connective tissue, making it prime for tearing under mechanical stress. 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. 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, partly as a result of the normal hormonal changes of pregnancy and partly due to<unk> ing of skin fibers. Many women experience striae gravidarum during their first pregnancy. Nearly 45% percent of women develop striae gravidarum before 24 weeks of gestation. Many women who develop lesions during the first pregnancy do not develop them during later pregnancies. Genetic factors such as genealogy and race also seem to be predictive in the appearance of striae.
Stretch marks
Wale mark
Spray-on skin
Copper beaten skull
Loop mark
Synechia 
Abasia
Brock string