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Keloid
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A keloid is a raised, firm scar, and what defines it is a geometric detail: it spreads beyond the edges of the wound that started it, and it does not regress over the years. It is like a repair that does not stop at the edge of the pothole and keeps spreading over the healthy asphalt.
What is thought to lie behind it is a signal that gets out of control. As a wound heals, macrophages, the defense cells that work in the injured area, release growth factors. One of them is transforming growth factor beta, and its job is to activate the fibroblasts, the cells that make collagen. When that signal falls out of balance, too much collagen is produced and it is laid down where it does not belong.
Under the microscope the difference shows. In a hypertrophic scar, which stays contained within the wound and may flatten over time, the collagen is arranged in a wavy, regular pattern. In a keloid there is no pattern: the collagen is laid down in no recognizable order.
In brief
A keloid is a raised, firm scar that spreads beyond the edges of the original injury and does not regress over time.
It is like a repair that does not stop at the edge of the pothole and keeps spreading over the healthy asphalt.
It is attributed to a misfiring of transforming growth factor beta, the signal macrophages use to activate fibroblasts to make collagen.
Under the microscope its collagen follows no pattern, unlike the wavy, regular pattern of a hypertrophic scar.
Sources (1)
- National Center for Biotechnology Information, StatPearls PublishingHypertrophic Scarring Keloids, StatPearlsPublished
This page explains the topic in general terms; it does not tell anyone what treatment to follow.
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