Keloid and hypertrophic scar !
Keloids and hypertrophic scars are raised scars from excess healing tissue. Keloids spread beyond the wound; hypertrophic scars stay within it.
Updated 2026-11-01
Structures involved
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Why it happens
- Fibrosis in organs: TGF-β and the myofibroblast
- Granulation tissue and scar formation
- Abnormal repair: chronic wounds, hypertrophic scar, keloid, contracture
- Healing of skin wounds: first and second intention
- Thermal injury: burns, hyperthermia and hypothermia
- Collagen synthesis
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What it is
Abnormal fibroproliferative healing responses with excess collagen. A hypertrophic scar is raised but stays within the borders of the original wound and often flattens over time. A keloid extends beyond the wound margins into normal skin, rarely regresses and frequently recurs after excision.
Who gets it
Keloids are much more common in people with darker skin (African and mixed ancestry), a large group in Colombia's Pacific and Caribbean regions, and peak between puberty and age 30. Hypertrophic scars are common after burns and surgery at any age. A family history is frequent in keloids.
Causes
- Skin injury of any kind: surgery, burns, lacerations, piercings, acne, vaccination, insect bites
- Genetic predisposition (familial keloids)
- Wound tension, infection and delayed healing
- Hormonal influences (keloids can grow in puberty and pregnancy)
Risk factors
- Darker skin and family history of keloids
- Age 10–30 years
- High-tension sites: chest (sternum), shoulders, upper back, earlobes, jawline
- Burns, infected or slow-healing wounds
- Ear piercing and severe acne
Pathophysiology
After injury, healing normally moves from inflammation to proliferation and then remodelling. In these scars, fibroblasts stay overactive, driven by growth factors such as TGF-beta and by mechanical tension, and produce excess collagen. Hypertrophic scars contain organised type III collagen nodules with myofibroblasts; keloids contain thick, disorganised hyalinised type I and III collagen bundles and invade surrounding dermis.
Classification
- Hypertrophic scar: confined to the wound, appears within weeks, may regress, linked to tension and burns
- Keloid: extends beyond the wound, appears months later, does not regress, high recurrence, linked to genetics and skin type
Symptoms and signs
- Firm, raised, shiny scar, pink-red early and later skin-coloured or darker
- Keloids: claw-like extension beyond the original wound, dumbbell shape on earlobes
- Itch and tenderness or pain, sometimes intense
- Contracture and reduced movement when hypertrophic scars cross joints (especially after burns)
- Cosmetic and emotional distress
Diagnosis
- Clinical
- Clinical, based on history of injury, timing, and whether the scar stays within or extends beyond the wound margins.
- Tests
- Biopsy only for atypical lesions (rapid growth, no history of trauma, ulceration) to exclude tumours; biopsy can itself trigger more keloid.
- Imaging
- Not needed. Photographs and scar scales are used to follow response.
Differential diagnosis
- Dermatofibroma and dermatofibrosarcoma protuberans
- Foreign-body granuloma (for example after piercing)
- Lobomycosis (keloid-like nodules in Amazon regions)
- Sarcoidosis in scars
- Squamous cell carcinoma arising in a scar
Goal of treatment
Prevent abnormal scarring in at-risk patients, and flatten, soften and relieve itch and pain in established scars while avoiding recurrence; combined treatments work better than one alone.
Treatment
- Conservative
- Silicone gel or sheets and pressure therapy (garments, pressure earrings), started soon after the wound closes; first-line for prevention and for early scars.
- Medical
- Intralesional corticosteroids are first-line for established keloids, often combined with 5-fluorouracil; topical corticosteroids or antihistamines for itch.
- Procedure
- Cryotherapy, pulsed-dye or fractional lasers and, in specialised centres, radiotherapy immediately after keloid excision.
- Surgical
- Excision of keloids only combined with adjuvant therapy (corticosteroid injections, pressure or radiotherapy), because excision alone recurs in most cases; scar revision and release of contractures for hypertrophic burn scars.
Complications
- Recurrence after treatment, often larger
- Chronic itch and pain
- Contractures and functional limitation
- Skin atrophy and hypopigmentation from corticosteroid injections
- Psychological distress
Prognosis
Hypertrophic scars often improve over 12–24 months. Keloids are persistent and recur often, but combination treatment can control symptoms and reduce size.
Prevention
- Avoid unnecessary procedures and piercings in predisposed people
- Close wounds with low tension and treat acne and wound infections early
- Use silicone and pressure early on wounds at risk
Test yourself
Think of the answer, then tap the question to see it.
What is the key clinical difference between a keloid and a hypertrophic scar?
A keloid extends beyond the original wound margins and rarely regresses; a hypertrophic scar stays within them and often improves.
What is the first-line treatment for an established keloid?
Intralesional corticosteroid injections, often combined with other measures.
Why is excision alone a poor treatment for keloids?
Recurrence after simple excision is very high, so surgery must be combined with adjuvant therapy.
Which are three high-risk sites for keloids?
Earlobes, the sternum/chest, shoulders and upper back, and the jawline.
Related conditions
- Acne vulgaris
- Hidradenitis suppurativa
- Abscess, furuncle and carbuncle
- Cutaneous squamous cell carcinoma
Educational information, not medical advice. For any symptom, see a health professional.
Sources: Keloids (MedlinePlus, US National Library of Medicine, 2026).
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