Stretch Marks

What are stretch marks?

Stretch marks or striae are indented streaks on the skin that are often found on the abdomen, buttocks, thighs, breasts, back, armpits and groin. They are more prevalent in women than in men, and more common in younger women than older women (R). Those with a family history of stretch marks and those who smoke are also more prone to developing stretch marks (R, R).

Stretch marks can be classified according to their appearance and what causes them (R).

• Striae rubrae: early stretch marks that are red and flat or slightly raised (R)
• Striae albae: mature stretch marks that have faded to a white or silvery colour, and appear atrophic and wrinkled (R)
• Striae nigrae: blackish stretch marks found in individuals with darker complexions (R, R)
• Striae caeruleae: bluish stretch marks observed in individuals treated with corticosteroids for a long time (R, R)
• Striae gravidarum: stretch marks that develop during pregnancy (R)
• Striae atrophicans: a known side effect of the long-term application of topical steroids (R)

What causes stretch marks?

Stretch marks are a form of scarring that arise due to the excessive stretching of the dermis. They often develop because of rapid changes in weight, such as during puberty, pregnancy and obesity (R, R). Stretch marks can also occur after breast augmentation, muscle hypertrophy in bodybuilders, and as a side effect of the prolonged use of corticosteroids (R, R, R).

Histologically, the formation of stretch marks is thought to involve the release of elastase enzymes from mast cells, which leads to the breakdown of elastin and a disruption of the elastic fibre network (R, R). Activated macrophages then envelope the fragmented elastic fibres (R). The expression of collagen, elastin and fibronectin are reduced (R), resulting in the skin becoming less firm, less elastic and less deformable (R, R). The epidermis also gradually atrophies and loses its rete ridges (R).

How are stretch marks measured?

Stretch marks can be scored for their severity by counting their number and the number of affected areas, measuring their size, and evaluating the intensity of their colour either subjectively or objectively through instruments and image analysis (R, R, R).