Keloid and Hypertrophic scars are pathological scars due to injury to this skin (deep enough to reach the reticular dermis) followed by aberrant or abnormal wound healing therein.
Definitions
Keloid
A keloid is a sharply elevated, irregular, progressively enlarging scar that extends beyond the boundaries of the original wound and caused by excessive deposition of abnormally thick collagen in the dermis during connective tissue repair.
Hypertrophic scar
A hypertrophic scar is a mildly elevated, erythematous, pruritic scar that does not extend beyond the boundaries of the original wound and caused by excessive deposition of normal collagen in the dermis during connective tissue repair.
Differences between Keloid and Hypertrophic scar
| Keloid | Hypertrophic scar | |
|---|---|---|
| Genetic, Racial predisposition | ✔️ Genetic: HLA- B14, B21, DR5, DQW3 Racial: ↑ Black, Hispanic, Asian | ❌ |
| Age, Sex | 10-30 years ✔️↑ Female | More in children ❌M=F |
| Onset, Duration | - Years to progressively develop (sometimes from trivial forgotten trauma/ lesions) - Long periods without regression | - Within 4 weeks of trauma - Grows for 6 months→ then Regresses |
| Appearance | - Red to purple to dark brown, firm - Extend beyond the margins of the wound - Irregular - Sharply elevated, often >4mm | - Pink to red, firm initially→ gradually softens - Do not extend beyond the wound margins - Takes the shape of the wound - Elevation, often <4 mm |
| Symptoms | Pruritus ± | ✔️ Pruritus, pain, hyperaesthesia |
| Common sites | Shoulder, sternal region, earlobe | Over joints |
| Association with scar-site tension | ❌ | ✔️ [So, common over joints] |
| Recurrence | ✔️ | ❌ |
| Histology | ↑ Type 1 & 3 collagen - pale and irregular - abnormally thick ✔️ ↑ Mucinous ground substance ❌ nodules | ↑ Type 3 collagen - oriented parallel to epidermal surface - normal thickness ❌ Scanty mucinous ground substance ✔️ ↑ nodules of myofibroblasts [So, scar contracture and regression happens] |
| Fibroblast activity | ✔️ ↑ Propyl hydroxylase (14 times ↑) & Alanine transaminase activity [So, excessive & thick collagen is produced] | ❌ |
💡Note: Fibroblast activity is more in Keloid while myofibroblast activity is more in Hypertrophic scar (Learn more about myofibroblasts🔗 to know the difference).
So, these are the differences between Keloid and Hypertrophic scar that will help us identify each since the Management of Keloid is quite different from that of hypertrophic scar.
Though they are different entities, sometimes clinically, we come across abnormal scar hypertrophy that has intermediate properties. These may be treated like a hypertrophic scar initially and if there is no regression, or there is progression- they may then be treated like a keloid.
Found another difference between a keloid and a hypertrophic scar? Do let us know in the comments section below. If you liked it, for more such articles- subscribe.
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