What distinguishes a hypertrophic scar from a keloid scar?

Distinguishing Hypertrophic Scars from Keloids

The correct answer is B. Hypertrophic scars may subside spontaneously, unlike keloids which do not regress with time.

Key Differences Between Hypertrophic Scars and Keloids

Hypertrophic scars and keloids represent two distinct types of abnormal scarring that occur following skin injury, though they have important clinical and histological differences:

Spontaneous Regression

• Hypertrophic scars typically show spontaneous regression over time (usually within 12-24 months) 1, 2
• Keloids do not regress spontaneously and often continue to grow progressively 1

Boundaries and Growth Pattern

• Hypertrophic scars remain confined within the boundaries of the original wound 2
• Keloids characteristically extend beyond the borders of the original wound, invading normal skin 3

Timing of Appearance

• Hypertrophic scars develop within weeks after injury
• Keloids may develop immediately after injury or appear in a delayed fashion, but not typically years later as suggested in option C 3

Familial Tendency

• Keloids have a stronger familial/genetic predisposition than hypertrophic scars 4
• Option A is incorrect because keloids, not hypertrophic scars, are more likely to be familial

Histological Differences

The histopathological differences between these two abnormal scars include:

• Hypertrophic scars contain:

  • Nodular structures with randomly organized collagen fibers
  • Alpha-smooth muscle actin (α-SMA) expressing myofibroblasts
  • Fine collagen fibers arranged in a random pattern 1

• Keloids contain:

  • Large, thick collagen fibers (keloidal collagen)
  • Collagen fibrils packed tightly together
  • Amorphous extracellular material surrounding fibroblastic cells
  • Rarely contain nodular structures 1

Clinical Implications

The distinction between hypertrophic scars and keloids is clinically important because:

1. Treatment approaches differ: Hypertrophic scars may respond to less aggressive interventions due to their potential for spontaneous regression
2. Prognosis differs: Hypertrophic scars have a better prognosis with higher likelihood of improvement over time
3. Surgical revision risks: Keloids are difficult to revise surgically and have high recurrence rates after excision 1

Common Pitfalls in Diagnosis

• Misdiagnosing a keloid as a hypertrophic scar may lead to inappropriate treatment expectations
• Both conditions can be pruritic and painful, so symptoms alone cannot distinguish between them
• The definitive distinction is often based on growth pattern (contained vs. extending beyond original wound)
• Histopathological examination may be necessary in ambiguous cases

Understanding these differences is essential for proper diagnosis and management of these abnormal scars, with hypertrophic scars having the distinctive characteristic of potential spontaneous regression over time.