Summary
Hypertrophic scars and keloids are cutaneous conditions caused by a disruption of wound healing in response to a dermal injury. Hyperproliferation, which manifests as thick, raised scar tissue, is caused by an increase in TGF-β expression, fibroblast proliferation, and collagen deposition. Hypertrophic scars typically form after a burn injury or surgical incision, whereas keloids have a genetic component and can occur after minor trauma. Diagnosis for children and adults is typically clinical; keloid scars have an irregular edge that extends beyond the original margins of the scar, whereas the borders of hypertrophic scars remain within the original margins. Skin biopsy is rarely necessary but can be considered if skin malignancy is suspected. Management is similar for children and adults, and prevention strategies are the most important method to reduce hyperproliferation. Although benign, both types of scars can be a cosmetic concern or cause debilitating contractures. Multiple treatment options are available and usually scars respond best to a combination of treatments. Hypertrophic scars generally regress within one year and respond well to treatment, whereas keloids commonly recur even with treatment.
Definition
-
Hypertrophic scar [1]
- An overgrowth of tissue that is thickened and raised within the boundaries of the original margins of a scar
- Usually regresses spontaneously
-
Keloid [1]
- An overgrowth of tissue that is thickened and raised with an irregular border that extends beyond the original margins of a scar
- Does not spontaneously regress and may recur if surgically excised
Epidemiology
- Age: can occur at any age but more commonly occurs between ∼10–30 years of age [2][3]
-
Genetic factors [1][2]
- Hypertrophic scars: A genetic component has not been observed.
- Keloids: Most common in black, Asian, and Hispanic individuals. [3]
Epidemiological data refers to the US, unless otherwise specified.
Etiology
- Not well understood [2][3][4]
- Possibly caused by an imbalance in wound healing, e.g:
- High fibroblast proliferation
- Increased collagen production
Risk factors
-
Risk factors for hypertrophic scars and keloids [2][5]
- Iatrogenic wounds: e.g., skin biopsy and surgical incisions [1][3][6]
- Lacerations [1]
- Burns (e.g., deep partial-thickness burn) [1][6][7]
- Presence of infection or foreign body [2][8]
-
Risk factors specific to keloids [1]
- Family history of keloid scars [2][3]
- Risk factors for delayed wound healing (e.g., history of radiation, corticosteroid use, poor nutrition) [3]
- Changes in hormones (e.g., during puberty and pregnancy) [3]
- Minor trauma (e.g., piercing, insect bites, injections, or acne) [6]
Hypertrophic scars are typically caused by burns and surgical incisions. [6]
Pathophysiology
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Common underlying pathophysiology [3][4]
- Increased TGF-β expression and fibroblast proliferation
- ↑ Type I collagen: type III collagen production
- ↓ Elastin deposition
-
Type-specific pathophysiology [5]
- Hypertrophic scars: threefold increase in the synthesis and parallel deposition of type III collagen
- Keloids: 20-fold increase in synthesis and unorganized deposition of type I collagen and type III collagen
Clinical features
| Clinical features of hypertrophic scars and keloids [1][2][3] | ||
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| Hypertrophic scar | Keloids | |
| Onset |
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| Location |
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| Borders |
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| Appearance |
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| Symptoms |
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| Clinical course |
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Keloid scars extended beyond the wound edges, while hypertrophic scars remain within. [5]
Diagnostics
- Diagnosis is usually clinical, based on appearance and history of trauma or surgery. [3][10]
- Skin biopsy can be performed if the diagnosis is uncertain or if there is suspicion of malignancy. [6][11]
Avoid skin biopsy of keloids unless malignancy is suspected, as the procedure can promote hyperproliferative scarring. [2]
Management
Approach [5]
- Monitor wounds to facilitate early identification and management.
- If hypertrophic or keloid scars develop in the first 6 months:
- Encourage patients to regularly moisturize.
- Apply silicone cream or dressings.
- Use pressure treatments.
- Widespread hypertrophic scars or growing keloid
- Refer to a specialist.
- Start intralesional corticosteroid injections.
- For scars present > 6 months after injury:
- Utilize all of the aforementioned treatments.
- Refer to a specialist for consideration of additional therapies and/or surgical excision.
Refer patients with contractures for surgical excision, regardless of how long the scar has been present. [11]
First-line treatments
The following treatments may be used alone or in combination; the choice of treatment will depend on the age of the scar, location, and patient preference.
Silicone treatments [12]
- Indications: hypertrophic and keloid scars of any age
- Options: creams or sheet dressings [10]
- Instructions for use: Apply to the affected area for at least 12 hours a day. [10]
- Contraindication: open wounds [1]
- Adverse effects: may cause allergic contact dermatitis, pruritus, or dryness [2]
Pressure therapy (compression therapy)
-
Indications
- All hypertrophic and keloid scars
- Commonly used for burn scars
-
Options: Referral for custom fitting may be required. [4]
- Pressure clips for the earlobes
- Compressive masks for the face
- Garments or bandages (e.g., spandex, elastic adhesive) for the body
- Instructions for use: Wear 23 hours a day with a pressure of 24–30 mm Hg. [1][13]
- Contraindications: severe peripheral arterial disease, decompensated heart failure [14]
Adherence to pressure therapy may be low because of discomfort, frequency of application, and cost. [1]
Intralesional corticosteroids
-
Indications: Use in addition to noninvasive treatment. [5]
- Keloid scars present > 4 weeks after injury
- Widespread hypertrophic scars present > 6 weeks after injury
- Linear hypertrophic scars present > 6 months after injury
- Options: include triamcinolone (most common) and betamethasone
-
Instructions for use
- Typically administered every 2–4 weeks for ≤ 6 months [1][2][3][5]
- Consider lidocaine or a topical anesthetic to reduce the pain associated with an intralesional injection. [1][15]
- Contraindications: active infection at scar site, allergy
- Adverse effects
Surgical excision
-
Indications: Consider only after trialing all other first-line treatments. [5]
- Linear or widespread hypertrophic scars present > 6 months after injury if causing functional impairment
- Any hypertrophic or keloid scars present > 12 months after injury
-
Options [1][4][5]
- Partial or complete removal of the scar with primary wound closure
- Skin graft or flaps for scar contractures
- Postsurgical management: Surgery should always be followed by preventive measures against hypertrophic or keloid scar recurrence. [5]
Additional therapies [1][5]
A specialist may combine any of the therapies below with first-line therapies to improve outcomes.
- Alternative intralesional injections (e.g., verapamil, fluorouracil, bleomycin) [1][2]
- Cryotherapy [5][16][17]
- Corticosteroid tape [10][18]
- Photodynamic therapy [2]
- Laser therapy (e.g., pulsed dye laser) [1][8]
- Imiquimod [1]
- Botulinum toxin A [2][8]
- Radiation therapy [3][19][20]
Avoid radiation therapy in children < 12 years of age and during pregnancy because of its potential carcinogenic effects. [4]
Prognosis
-
Hypertrophic scars
- Frequently regress within 1 year without treatment [3]
- Typically respond well to treatment, if needed [1]
-
Keloids
- Respond better to early treatment [1][3]
- Flatten after treatment with intralesional corticosteroid injections in up to 50% of cases [1]
- Nearly always recur after surgical excision unless other therapies are also administered [1][2]
Prevention
General principles [5]
- Prevention strategies are the most effective way to avoid hyperproliferative scarring.
- All individuals: Basic preventive measures should be used during the first 6 weeks after injury.
- For individuals with risk factors for hypertrophic and keloid scars, the following precautions are recommended:
- Avoidance of elective surgeries and piercings
- Frequent wound assessments for early identification
Prevention strategies [1][3][5]
All wounds
- Adequate wound care (e.g., frequent cleaning) during wound healing (see “Wound treatment”) [2]
- Moisturizing the scar
- Use of photoprotective measures until the scar matures
- To minimize iatrogenic scarring, when possible, make surgical incisions parallel to relaxed skin tension lines. [5]
High-risk wounds for hyperproliferative scarring
- Features of high-risk wounds:
- Occurrence in individuals with risk factors for hypertrophic or keloid scars
- Located in an area that is high risk or under tension
- Caused by burns [21]
- Management of incisions can reduce the risk of hyperproliferative scars, e.g.:
- Surgical techniques (e.g., Z-plasty) [2][3][5]
- Immobilization: for surgical incisions over areas of tension (e.g., joints) [3]
- Surgical taping [3]
- Microporous paper tape: for use after cesarean delivery [9]
- During the first 6 months, patients with high-risk wounds should: [5]
- Have regular reviews
- Receive preventive silicone treatment and/or pressure therapy (see “Management of hypertrophic and keloid scars”)
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