Hypertrophic scars
Introduction
Hypertrophic scars are a type of abnormal wound healing characterized by excessive collagen deposition leading to raised, thickened scars that remain within the boundaries of the original wound. These scars are often red, itchy, and can be painful. They differ from keloid scars, which extend beyond the original wound boundaries. Hypertrophic scars are a common concern in dermatology and plastic surgery due to their aesthetic and functional implications.
Pathophysiology
The formation of hypertrophic scars involves a complex interplay of cellular and molecular mechanisms. The primary factor is the overproduction of collagen, particularly type I and type III collagen, by fibroblasts. This process is regulated by various cytokines and growth factors, including transforming growth factor-beta (TGF-β), platelet-derived growth factor (PDGF), and fibroblast growth factor (FGF).
During normal wound healing, collagen synthesis and degradation are balanced. However, in hypertrophic scars, this balance is disrupted, leading to excessive collagen accumulation. The extracellular matrix (ECM) becomes dense and disorganized, contributing to the raised appearance of the scar.
Clinical Presentation
Hypertrophic scars typically present as raised, erythematous, and firm lesions confined to the area of the original injury. They often develop within weeks to months after the initial trauma. Common symptoms include pruritus (itching), pain, and restricted movement if the scar is located near a joint.
Risk Factors
Several factors increase the likelihood of developing hypertrophic scars:
- **Genetic predisposition:** Individuals with a family history of hypertrophic scarring are at higher risk.
- **Skin type:** Darker skin types (Fitzpatrick skin types IV to VI) are more prone to hypertrophic scarring.
- **Wound characteristics:** Deep wounds, wounds under tension, and wounds in areas of high mobility (e.g., shoulders, knees) are more likely to develop hypertrophic scars.
- **Infection and inflammation:** Prolonged inflammation and infection can exacerbate scar formation.
Diagnosis
Diagnosis of hypertrophic scars is primarily clinical, based on the appearance and history of the lesion. Dermoscopy can aid in the evaluation by providing a detailed view of the scar's vascular and collagen structures. In some cases, a biopsy may be performed to differentiate hypertrophic scars from other conditions, such as keloids or dermatofibromas.
Treatment
The management of hypertrophic scars involves a combination of non-invasive and invasive techniques:
Non-Invasive Treatments
- **Silicone gel sheets and creams:** These are commonly used to flatten and soften scars. They work by hydrating the scar tissue and modulating collagen production.
- **Pressure therapy:** Applying pressure garments can help reduce scar thickness, particularly in burn patients.
- **Intralesional corticosteroids:** Injections of corticosteroids, such as triamcinolone acetonide, can decrease inflammation and collagen synthesis, leading to scar regression.
- **Laser therapy:** Pulsed dye laser (PDL) and fractional CO2 laser are effective in reducing scar redness and thickness by targeting blood vessels and promoting collagen remodeling.
Invasive Treatments
- **Surgical excision:** Reserved for severe cases, surgical removal of the scar followed by appropriate wound care can improve outcomes. However, there is a risk of recurrence.
- **Radiotherapy:** Low-dose radiotherapy can be used post-surgery to prevent recurrence, particularly in high-risk patients.
- **Cryotherapy:** Freezing the scar tissue with liquid nitrogen can reduce its size and improve texture.
Prognosis
The prognosis for hypertrophic scars varies. Many scars improve over time, becoming less noticeable. However, some may persist and require ongoing treatment. Early intervention and consistent management are crucial for optimal outcomes.
Prevention
Preventive measures focus on minimizing risk factors and promoting optimal wound healing:
- **Proper wound care:** Keeping the wound clean and moist, and avoiding tension on the wound edges.
- **Early use of silicone gel sheets:** Applying silicone products as soon as the wound has epithelialized can prevent excessive scar formation.
- **Avoiding sun exposure:** Protecting the healing wound from UV radiation can reduce hyperpigmentation and scar formation.