Reflecting on acne scarring for Acne Awareness Month

Acne is a disease of the hair follicle and its associated sebaceous gland, collectively known as the pilosebaceous unit. Abnormal keratinisation, excess sebum production and overgrowth of the anaerobic bacteria Cutibacterium Acnes leads to rupture of the hair follicle and tissue injury. This cascade of events stimulates wound healing, a process that can ultimately lead to scar formation.

The initial steps of wound healing involve migration of inflammatory cells to the site of tissue injury, production of type I and type III collagen by fibroblasts and remodelling of the extracellular matrix. Fibroblasts and keratinocytes produce matrix metalloproteinases (MMPs) and tissue inhibitors of MMPs. The former are lytic enzymes that break down the extracellular matrix. An imbalance between the two groups of enzymes can lead to excess collagen production and hypertrophic (elevated) scars or excess degradation of extracellular matrix and atrophic (depressed) scars. There are three types of atrophic scars: ice pick, boxcar and rolling.