Which of the following is not true about keloid ?
**Core Concept**
Keloids are a type of raised, thick scarring that occurs after skin injury, characterized by an abnormal proliferation of fibroblasts and an excessive deposition of collagen. This process is often driven by an imbalance between collagen synthesis and degradation, leading to a persistent and sometimes itchy or painful scar.
**Why the Correct Answer is Right**
Keloids are indeed characterized by an overproduction of collagen, which is typically a result of an abnormal activation of fibroblasts and an upregulation of collagen-producing genes, such as COL1A1 and COL3A1. The excessive collagen deposition in keloids is often accompanied by an increased expression of transforming growth factor-beta (TGF-β), which promotes fibrosis and scar formation.
**Why Each Wrong Option is Incorrect**
**Option A:** Keloids are typically associated with an overproduction of collagen, making this statement true.
**Option B:** Keloids are often itchy, painful, or tender to the touch, making this statement true.
**Option C:** Keloids can occur after any skin injury, including minor cuts, scrapes, or burns, making this statement true.
**Clinical Pearl / High-Yield Fact**
A key characteristic of keloids is their tendency to extend beyond the original site of injury, often leading to a larger and more noticeable scar. This is due to the abnormal proliferation of fibroblasts and the excessive deposition of collagen, which can lead to a persistent and sometimes disfiguring scar.
**Correct Answer: D.**