Wound Healing Acne scarring

Acne scars can be broken down into three main categories, depending on whether there is a net loss or gain of collagen: atrophic; hypertrophic, and keloidal. Of people with acne scars, 81–90% have scars associated with a loss of collagen (atrophic scars) compared with a minority who develop hypertrophic scars and keloids.

Atrophic scars can be further sub-classified into ice pick; rolling; and boxcar. The exact prevalence of each scar type is hard to calculate but some estimations report that within atrophic scars, the ice pick type represents 60–75%, boxcar 20–30%, and rolling scars 20–25%.

Ice pick scars are narrow, sharply demarcated, V-shaped tracts, <2 mm in diameter, that usually extend into the deep dermis or the subcutaneous layer. Boxcar scars are wider 1–4 mm in diameter, U-shaped tracts, with sharp, vertical edges that extend 0.1–0.5 mm into the dermis. Rolling scars are characterized by dermal tethering of the dermis to the subcutis. They are generally ≥4 mm in diameter, irregular, with a rolling or undulating appearance.

Hypertrophic scars are typically raised and firm scars that remain within the borders of the original site of injury. In contrast, keloid scars form as reddish-purple papules and nodules that extend beyond the borders of the original wound.

Scar classification is important as it can help guide treatment options. Ice pick scars can extend deep into the dermis, which makes them resistant to conventional skin-resurfacing options. Rolling scars are wider and have fibrous anchoring to the subcutis, thus necessitating treatment at a sub-dermal level. Shallow boxcar scars are more amenable to skin resurfacing treatments whereas deeper boxcar scars are more resistant to such superficial treatments