Which of the following is NOT a feature of keloids?
**Core Concept**
Keloids are a type of raised, thickened scar tissue that forms after skin injury, characterized by an overgrowth of collagen and other skin components. They are distinct from hypertrophic scars, which are also raised but do not extend beyond the original wound boundaries.
**Why the Correct Answer is Right**
Keloids are typically distinguished by their ability to grow beyond the original wound site, in contrast to hypertrophic scars. This is due to an abnormal response to injury, involving an increased expression of growth factors and an overactive collagen synthesis pathway. The key enzymes involved in this process include collagenase and matrix metalloproteinases, which are upregulated in keloid tissue. The resulting scar tissue is more rigid and fibrotic than normal skin.
**Why Each Wrong Option is Incorrect**
**Option A:** Keloids can indeed be painful, but this is not a distinguishing feature that sets them apart from other types of scars.
**Option B:** Keloids are actually more common in individuals with darker skin types, due to genetic predisposition.
**Option C:** Keloids are indeed characterized by an overgrowth of collagen, which is a key component of their formation.
**Clinical Pearl / High-Yield Fact**
Keloids can be treated with a variety of methods, including topical silicone gel, intralesional corticosteroids, and surgical excision, but recurrence is common due to the underlying genetic predisposition.
**Correct Answer:** C.