| PHOTOTHERAPY | ARTICLE boys affected), but especially during pregnancy
(60–70% of primipara women, usually occurring in 6–7th
month), and as a function of variation in body
weight. Other causal factors in the formation of stretch marks have also been identified: ■ In cases of excessive adrenocortical activity or hyperadrenocorticism
■ Inherited abnormalities of connective tissue ■ Metabolic and endocrine diseases (malnutrition, obesity, prolonged treatment with glucocorticoids, Cushing syndrome)
■ High-level athletes (and particularly bodybuilders). Depigmenting creams, often used in Africa, and which
are usually based on corticosteroids, and hydroquinone also trigger stretch marks, even many years after application2–8
.
Which parts of the body may be affected? Stretch marks appear in areas where the skin is subjected to excessive tension and in cases of weakening of the dermis, either constitutionally or by metabolic and hormonal influences for example. They occur mainly on the breasts, abdomen and flanks, upper and inner thighs, hips, buttocks, lower back, and sometimes on the shoulders, underarms, upper arms to elbows, calves and knees. Stretch marks are essentially an aesthetic problem; however, when expanded, they may ulcerate or tear as a result of an accident or excessive tension.
The role of corticosteroids in the appearance of stretch marks Corticosteroids administered orally or topically can eventually block the proliferation and the fibroblast cell metabolism, leading to a decrease in collagen fibres. This decrease varies according to the chemical structure of steroid compounds and the type of anti-inflammatory response they trigger. Corticosteroid use is also linked with a decrease in skin
thickness that is not directly related to a decrease in collagen. As we age, however, a significant decrease in collagen is by no means accompanied by the formation of stretch marks. There is also an inevitable decrease in stretch resistance, which could explain the formation and appearance of cortico-dependent stretch marks9 seem to be caused by physical changes in the structure of
. They collagen, rather than variations in the amount of collagen.
Historical studies Stretch marks were first described in 1869, by Troiser and M• n• trier10
beginning of the 20th
, as a trivial and harmless disorder. At the century, researchers based the close
relationship between the formation of stretch marks and a range of physiological disorders, such as tuberculosis, typhoid fever, rheumatic fever or chronic infections. Simpson, in 1950, showed that adrenocortical hyperactivity following prolonged or systematic topic treatments with corticosteroids induced the formation of stretch marks23
. Shelley and Cohen11 showed that stretch marks appear
frequently during a variety of skin disorders, and are often associated with physiological processes, such as pregnancy, obesity, rapid weight gain, and growth in adolescents. In 1980, Arem and Kisher12
spoke of tissue in
the intermediate transition phase between hypertrophic tissue and a scar.
Etiopathogenic theories: disease fibroblast? The fibroblast is an isolated cell within the connective tissue. It synthesises the majority of extracellular matrix molecules ® collagen, elastin, fibronectin, proteoglycans, substances located between the cells ® the major components of connective tissue, but also the vast majority of the mass of a body. They come from the division of mesenchymal stem cells of fusiform shape. These cells have the ability to divide (heterotypic division) by mitosis to produce two different cells: ■ A stem cell which will remain a stem cell, with the ability to divide again
■ A cell that will return via a differentiation programme. These cells can be fibroblasts, but also myofibroblasts, adipofibroblasts, chondroblasts, cementoblasts, odontoblasts, and osteoblasts. Stretch marks result from a combination of factors, but
first and foremost, today it is acknowledged that stretch marks are associated with a disease of fibroblasts that interrupts the production of collagen fibres and elastin in the furrows of the stretch marks. Corticosteroid excess eventually blocks the proliferation and metabolism of fibroblasts during physiological or pathological events, and act as a cofactor of enzymatic processes.
Stretch marks appear
in areas where the skin is subjected to excessive tension and in cases of weakening of the dermis, either constitutionally or by metabolic and hormonal influences.
Figure 1 Patient one (A) before and (B) after treatment
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