Keloids and hypertrophic scars

Keloids and hypertrophic scars are cutaneous fibroproliferative disorders resulting from abnormal wound healing, characterized by excessive collagen deposition. In keloids, abnormal proliferation of the dermal layer extends beyond the original wound borders, while in hypertrophic scars, it remains within the original wound boundaries.

The pathogenesis of keloids and hypertrophic scars is not fully understood but involves dysregulation of wound healing phases, excessive fibroblast activity, and collagen deposition. Injury to the reticular dermis from surgery, burns, or trauma is a key trigger, while minor injuries like folliculitis or insect bites can induce keloids in susceptible individuals. Hypertrophic scars and keloids develop in predisposed individuals following injury to the reticular dermis, including surgical incisions, burns, or trauma. In highly susceptible individuals, minor injuries, such as folliculitis or insect bites, may also lead to keloid formation. Multiple cell types, including fibroblasts, myofibroblasts, keratinocytes, melanocytes, mast cells, and endothelial cells, contribute to scarring. Endothelial dysfunction during inflammation increases vascular permeability, promoting prolonged inflammation and fibrosis. Pathologic scars involve elevated cytokines and growth factors, such as transforming growth factor beta, VEGF, platelet-derived growth factor, IL-6, and IL-8.

Keloids and hypertrophic scars most commonly appear between ages 10 and 30 years. The epidemiology of keloids varies, with reported annual incidence ranging from 0.09% in England and 0.15% in Taiwan to as high as 4.5% and 16% in African and Hispanic populations. The incidence of hypertrophic scars is reported at 40-70% after surgery and over 90% after burns.

Inciting factors include various dermal injuries, especially surgery, trauma, and burns. Risk factors include genetic predisposition, family history, African, Hispanic, and Asian origin, young age (10-30 years), and pregnancy.

Hypertrophic scars and keloids appear as firm, raised, erythematous lesions with a glossy surface, typically red in White individuals and purple to black in Black individuals. Keloids commonly form unique shapes, influenced by local tension forces. Hypertrophic scars typically grow for 3-6 months before stabilizing and regressing, particularly in patients with a lower risk of pathologic scarring. Pain and itching are prominent symptoms of keloids and are often more intense than in hypertrophic scars.