Based on Scott brown and sataloff otolaryngology and head neck surgery
Keloids and hypertrophic scars are types of abnormal wound healing that result in excessive tissue formation following skin injuries. Understanding the distinctions, pathophysiology, treatment, and prevention of these scars is important in clinical practice, especially in fields like dermatology, plastic surgery, and wound care. This lecture will cover the key aspects of keloids and hypertrophic scars in detail.
I. Overview of Wound Healing:
Wound healing is a complex process involving inflammation, proliferation, and remodeling phases. Normally, after an injury, the body repairs the skin by producing collagen to close the wound. In some cases, this process can become dysregulated, leading to excessive scar formation.
II. Definitions:
• Keloids: Keloids are thick, raised scars that extend beyond the original boundaries of the wound. They can continue to grow over time and do not regress spontaneously.
• Hypertrophic Scars: These are raised scars that remain within the boundaries of the original wound. They may improve over time without intervention but can be problematic due to their appearance or associated symptoms.
III. Pathophysiology:
1. Keloids:
• Excessive Collagen Production: Keloids result from an overproduction of type I and type III collagen due to prolonged inflammatory responses and fibroblast proliferation.
• Genetic Predisposition: There is often a genetic component, with higher prevalence in individuals of African, Hispanic, and Asian descent.
• Altered Cellular Activity: Increased fibroblast activity and abnormal cytokine signaling (e.g., TGF-β) contribute to keloid formation.
• Risk Factors: Include darker skin pigmentation, family history, and injuries in specific body areas (e.g., chest, shoulders, earlobes).
2. Hypertrophic Scars:
• Localized Overproduction of Collagen: Similar to keloids, hypertrophic scars are due to excessive collagen but are confined to the wound site.
• Shorter Inflammatory Phase: Compared to keloids, hypertrophic scars have a more regulated healing process.
• Risk Factors: Include tension on the wound, infection, and delayed wound healing.
IV. Clinical Features:
1. Keloids:
• Appearance: Raised, firm, and shiny with a reddish or dark color.
• Growth: Extend beyond the wound margins and do not regress.
• Symptoms: Can be itchy, painful, and cause discomfort or restricted movement depending on location.
• Common Sites: Chest, shoulders, upper back, earlobes, and cheeks.
2. Hypertrophic Scars:
• Appearance: Raised, red, and firm but confined to the original wound boundary.
• Growth: Do not extend beyond the wound margins and may flatten and fade over time.
• Symptoms: Often associated with itching or tightness but generally less painful than keloids.
• Common Sites: Areas subject to tension, such as over joints or on the chest.
