Keloids are pathological scars that are characterized histologically by an overwhelming aggregation of fibroblasts and collagen type I within the inflammatory reticular dermis. Their clinical characteristics include continuous growth and invasion into the neighboring healthy skin beyond the original wound boundary via an erythematous and pruritic leading edge. They also show a strong tendency to recur when they are surgically excised in the absence of adjuvant therapies. Despite the fact that keloids are common throughout the world, their epidemiology has not been adequately investigated. In this chapter, we will summarize the limited epidemiological data on keloids that exists to date in terms of: (1) the demographic distribution of keloids, mainly on the geographical regions and ethnic racies; (2) the internal genetic factors that shape keloid rates; and (3) the external environmental factors that influence keloid epidemiology. The aim of the chapter is to facilitate a greater understanding of the complexity and diversity of keloids from an epidemiological perspective, thereby potentiating further and deeper explorations into individualized strategies that prevent and treat keloids.
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