Stretchmarks are a kind of small fissures similar to soft scars formed on the skin, that are due to a reduction in the thickness of the skin secondary layer to a reduced production, at this level, of collagen and elastin by the fibroblasts, cells that make the skin.
They appear when the skin is subjected to an exaggerated distension, extension then following loss of volume.
Very frequently, they are seen amongst in more than 50% of the young population: 25% of girls and 10% of boys at puberty, and 50 to 70% of pregnant women.
Histologically, there is an inflammatory infiltrate at the level of recent stretch marks and a breakage of dermal collagen at the level of the older stretch marks with neocollagenesis and thickening of the elastic fibers.
The circumstances of onset are puberty, pregnancy, obesity, taking certain medications.