What Are Hypertrophic Scars ?

A hypertrophic scar is characterized by excessive collagen deposition confined to the original wound margins, often presenting as raised, erythematous, and firm tissue. Onset typically occurs within weeks post injury, with a proliferative phase lasting for 3–6 months, followed by gradual regression over a period of a few years.

Complete scar maturation may take up to 2 years. The risk factors include young age, infection, skin stretch and anatomic location (i.e. axilla, neck, small finger). Frequently affected sites include convex facial regions and areas subject to high tension or mobility. (1)

Pathophysiology of Hypertrophic Scarring

Hypertrophic scarring arises from dysregulation within the normal wound healing process, which progresses through inflammation, proliferation, and remodeling phases.

Following injury, platelet degranulation and activation of clotting and complement cascades initiate hemostasis and release cytokines such as transforming growth factor β (TGF-β), platelet-derived growth factor (PDGF), and epidermal growth factor (EGF).

These mediate recruitment of inflammatory and reparative cells, including neutrophils, macrophages, fibroblasts, and endothelial cells. Fibroblasts synthesize extracellular matrix (ECM)components to form granulation tissue, while myofibroblasts contribute to wound contraction.

The transformation of a wound clot into granulation tissue thus requires a delicate balance between ECM protein deposition and degradation, and when this process is disrupted, abnormalities in scarring appear.

In hypertrophic scarring, this tightly regulated sequence becomes disrupted. Prolonged inflammation, persistent fibroblast activation, and excessive collagen (mainly type III) deposition occur alongside impaired ECM remodeling.

Key drivers include sustained TGF-β signaling and reduced apoptosis of myofibroblasts. The result is a raised, erythematous scar confined to the wound margins, with increased vascularity and collagen density. This reflects an imbalance between ECM synthesis and degradation during the remodeling phase. (2)

Key Pathological Features

  • Prolonged inflammatory response
  • Exaggerated fibroblast activity
  • Excess deposition of type III collagen
  • Disorganized collagen framework
  • Persistent myofibroblast contraction (3)

Clinical Features

Hypertrophic scars (HTSs) are typically raised, though seldom more than 4 mm above the skin surface. The scars are firm in consistency, red or pink in color, and often pruritic. They remain confined within the original wound boundaries.


Histologically, HTSs are characterized by abundant type III collagen arranged parallel to the epidermis, with prominent collagen nodules and thick extracellular collagen bundles. (4)

Epidemiology

Hypertrophic scars lack a clear genetic predisposition but are more frequently observed in individuals with darker skin tones and in areas of high mechanical tension. Incidence rates range from 39–68 percent post surgery and 33–91 percent following burns. While some studies suggest higher rates in women, others report no sex-based difference.


Hypertrophic scars are more common in individuals aged 11–30, likely due to increased epidermal turnover, heightened collagen synthesis, greater skin tension, and a more robust immune response compared to older adults. (5)

Conventional Treatment Options

Established therapies for hypertrophic scars aim to reduce bulk, alleviate stiffness, and normalize pigmentation. These include:

  • Occlusive Dressings: Silicone-based dressings improve scar hydration and flattening via occlusion.
  • Compression Therapy: Pressure garments reduce scar height through local hypoxia.
  • Intralesional Steroids: Corticosteroids decrease the scar volume and components of connective tissue.
  • Excision: Excision if done only hypertrophic scars and keloids often result in recurrence by 45-100 percent.
  • Radiation Therapy: Radiation therapy is considered a safe and efficacious option for modality in recurrence reduction.
  • Laser Therapy: CO₂, Nd:YAG, and Argon lasers reduce scar thickness and erythema.
  • Interferon Injections: Intralesional interferon -gamma and -alpha 2b help reduce scar height and recurrence.

References

  1. Source: https://www.sciencedirect.com/topics/medicine-and-dentistry/hypertrophic scar
    Agarwal S, Sorkin M, Levi B. Heterotopic Ossification and Hypertrophic Scars. Clin Plast Surg. 2017 Oct;44(4):749-755 Gauglitz GG, Korting HC, Pavicic T, Ruzicka T, Jeschke MG. Hypertrophic scarring and keloids: pathomechanisms and current and emerging treatment strategies. Mol Med. 2011 Jan-Feb;17(1-2):113-25 Mony MP, Harmon KA, Hess R, Dorafshar AH, Shafikhani SH. An Updated Review of Hypertrophic Scarring. Cells. 2023 Feb 21;12(5):678.

  2. Source: https://molmed.biomedcentral.com/articles/10.2119/molmed.2009.00153 https://pmc.ncbi.nlm.nih.gov/articles/PMC10000648/ Mony MP, Harmon KA, Hess R, Dorafshar AH, Shafikhani SH. An Updated Review of Hypertrophic Scarring. Cells. 2023 Feb 21;12(5):678. Gauglitz GG, Korting HC, Pavicic T, Ruzicka T, Jeschke MG. Hypertrophic scarring and keloids: pathomechanisms and current and emerging treatment strategies. Mol Med. 2011 Jan-Feb;17(1-2):113-25.

  3. Source: https://molmed.biomedcentral.com/articles/10.2119/molmed.2009.00153 Gauglitz GG, Korting HC, Pavicic T, Ruzicka T, Jeschke MG. Hypertrophic scarring and keloids: pathomechanisms and current and emerging treatment strategies. Mol Med. 2011 Jan-Feb;17(1-2):113-25

  4. Source:https://pmc.ncbi.nlm.nih.gov/articles/PMC4129552/#:~:text=HTSs%20are%20usu ally%20raised%2C%20although,extracellular%20collagen%20filaments%20(11). [Introduction > Distinguishing hypertrophic scars from keloids] Rabello FB, Souza CD, Farina Júnior JA. Update on hypertrophic scar treatment. Clinics (Sao Paulo). 2014 Aug;69(8):565-73

  5. Source: https://www.ncbi.nlm.nih.gov/books/NBK537058/ [Epidemiology] Carswell L, Borger J. Hypertrophic Scarring Keloids. [Updated 2023 Aug 8]. In: StatPearls [Internet]. Treasure Island (FL): StatPearls Publishing; 2025 Jan-. Available from: https://www.ncbi.nlm.nih.gov/books/NBK537058/

  6. Source:https://pmc.ncbi.nlm.nih.gov/articles/PMC6991940/#:~:text=How%20the%20inter vention%20might%20work,be%20worn%20until%20scar%20maturation. [For Compression Therapy] https://pubmed.ncbi.nlm.nih.gov/9889433/#:~:text=Although%20the%20most%20commo nly%20used,number%20of%20post%2Doperative%20recurrences. - Abstract Harris IM, Lee KC, Deeks JJ, Moore DJ, Moiemen NS, Dretzke J. Pressure‐garment therapy for preventing hypertrophic scarring after burn injury. Cochrane Database Syst Rev. 2020 Jan 30;2020(1):CD013530. Berman B, Flores F. The treatment of hypertrophic scars and keloids. Eur J Dermatol. 1998 Dec;8(8):591-5.