مقاله انگلیسی رایگان در مورد پرتودرمانی برای بیماری های خوش خیم – الزویر 2020

Keloids are benign dermal disorders that consist of raised scars formed from excessive tissue proliferation and excess collagen in the skin, mostly resulting from pathologic wound healing after injuries to the deep dermis, including surgery, trauma, and burn injuries.1 Some other inciting events include body piercings, acne, insect bites, and vaccinations. However, some keloids form spontaneously and usually in areas with high skin tension, such as presternal, back, and posterior neck regions. Although sometimes painful and pruritic, keloids are usually asymptomatic and mainly of cosmetic concern.2–4 The exact pathophysiologic mechanisms causing keloid formation are unknown. Unlike hypertrophic scars, keloids extend beyond the boundary of the original site of injury. Fibroblasts in keloids seem to have different properties compared with normal skin of hypertrophic scars, because they show greater capacity to proliferate and produce high levels of primarily type I collagen, elastin, fibronectin, and proteoglycan.5–7 In contrast, hypertrophic scars only show a modest increase in collagen production and respond normally to growth factors.8 Several studies have shown an association between transforming growth factor-b and increased collagen or fibronectin synthesis by keloid fibroblasts.8–10 It is hypothesized that radiation acts on fibroblasts to prevent their repopulation after excision, modulates humoral or cellular factors that would otherwise recruit or stimulate fibroblasts, or inhibits angiogenesis. Keloids are common, occurring in 5% to 15% of wounds and affecting both sexes equally.13 They mainly affect people 10 to 30 years old14 and are more commonly seen in those with family history of keloids.15 Marneros and colleagues16 studied 14 pedigrees and determined that keloids were an autosomal dominant entity with incomplete penetrance and variable expression. Keloids are more prominent in those with darker skin phototypes, such as black and Hispanic populations, in which the incidence is 4.5% to 16%.17,18 Fig. 1 shows a common keloid occurring after ear piercing in a female African American.