Differences Between Keloid and Hypertrophic Scar
The key difference between keloids and hypertrophic scars is that keloids grow beyond the original wound boundaries, while hypertrophic scars remain confined within the original injury margins. 1
Clinical Characteristics
Keloids
- Extend beyond the original wound boundaries
- Continue to grow over time without regression
- May appear months to years after initial injury
- Often pruritic, painful, and tender
- Commonly occur on earlobes, shoulders, chest, and back
- Higher prevalence in darker skin types
- Strong genetic predisposition
- Keloidal collagen (thick, hyalinized collagen bundles) on histology 2, 1
Hypertrophic Scars
- Remain confined within the original wound boundaries
- Typically appear within weeks after injury
- Often regress spontaneously over 12-18 months
- Less symptomatic than keloids
- More common in areas of high tension (joints, chest)
- Can occur in any skin type
- Dermal nodules with α-SMA-positive myofibroblasts on histology 3, 1
Pathophysiology
Both keloids and hypertrophic scars represent aberrant wound healing with chronic inflammation in the reticular dermis. However, they differ in:
- Inflammatory response: Keloids show more prolonged and intense inflammation 3
- Collagen production: Keloids have excessive, disorganized collagen deposition
- Growth factors: Different expression patterns of TGF-β and PDGF 2
- Genetic factors: Keloids have stronger genetic predisposition with familial patterns 4
Histological Differences
| Feature | Hypertrophic Scar | Keloid |
|---|---|---|
| Collagen | Fine, parallel bundles | Thick, hyalinized "keloidal" collagen |
| Nodules | Present | May be absent |
| Vascularity | Higher | Lower |
| Fibroblasts | More organized | Haphazard arrangement |
Treatment Approaches
Hypertrophic Scars
- First-line: Silicone sheets/gel, compression therapy
- Second-line: Intralesional corticosteroids (triamcinolone 10-40 mg/mL)
- Refractory cases: Surgical excision with tension-free closure 5
Keloids
- First-line: Intralesional triamcinolone (40 mg/mL) combined with cryotherapy
- Second-line: Combination therapy (TAC + 5-FU or TAC + cryotherapy)
- Refractory cases: Surgical excision followed by radiation and steroid tape/plaster 5, 4
Prevention
- Patients with history of keloids should avoid body modifications that puncture the skin 6
- Prophylactic measures after surgery in high-risk patients include:
- Tension-free wound closure
- Silicone sheets/gel application
- Prophylactic steroid injections
- Compression therapy
Pitfalls in Diagnosis and Management
- Misdiagnosis can lead to inappropriate treatment approaches
- Keloids may be mistaken for hypertrophic scars if seen early in development
- Hypertrophic scars may be overtreated if mistaken for keloids
- Keloid treatment requires longer follow-up due to high recurrence rates
- Treatments that work for hypertrophic scars may be ineffective for keloids
Complications
- Keloids may develop hypertrophic scarring after treatment 6
- Both can cause significant functional and cosmetic impairment
- Psychological impact should be addressed as part of treatment
- Recurrence rates for keloids remain high (50-80%) despite treatment
Understanding the fundamental differences between keloids and hypertrophic scars is essential for proper diagnosis and management, as they require different therapeutic approaches despite their similar appearance.