Hypertrophic vs. Keloid Scar

Abnormal scars can be defined as Hypertrophic or Keloid. They do not follow normal scar evolution and difference from clinical, morphological and treatment perspective.
Hypertrophic vs. Keloid Scar

Normal scars follow a cycle of matrix proliferation, stabilisation and maturation. Hypertrophic scars follow a more protracted course, whilst Keloid scars do not follow this cycle of evolution. They are both abnormal scars.

The main differences between hypertrophic and keloid scars can be remembered by the mnemonic BAD SCAR.


Clinical Differences

There may be symptoms of pain, tenderness, and pruritus.

Hypertrophic Scar
Hypertrophic Scar
Keloid Scar
Keloid Scar

Morphological Differences

The diagnosis of keloids and hypertrophic scars is clinical. If uncertain, consider a biopsy.

HypertrophicKeloid
CollagenType IIIType I + III
FibersParallel to epidermisRandom to epidermis
MyofibroblastsPresentAbsent
Cell NumberIncreasedDecreased in nodules
Increased in periphery
Histological and Morphological differences of Keloid, Hypertrophic and Normal scars

Natural History

A normal scar increases in height and firmness during matrix proliferation, The scar then stabilises for 6-9 months before becoming flat and smooth during maturation. Hypertrophic scarring begins like normal scarring, except with a prolonged time course. Keloid scarring does not follow the normal scar evolution pattern.

HypertrophicKeloid
ResolveSpontaneous (most)No
Recur post-SurgeryNoYes
Scar Healing

The different forms of treatment options and their varying success rates emphasises the difference between keloid and hypertrophic scars. It also suggests a significant heterogeneity within each category of the scar.


Sources

  1. Hypertrophic response and keloid diathesis: two very different forms of scar. Plast Reconstr Surg. 2005 Dec;116(7):150e-157e. Burd A, Huang L.
  2. Duration of Scar Maturation: Retrospective Analyses of 361 Hypertrophic Scars Over 5 Years. Advances in Skin & Wound Care: January 2019. Kant, Sander, MD
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