A keloid is an abnormal proliferation of scar tissue which forms at the site of injury, rises above the skin level and projects beyond original wound margins, and does not regress.
Keloid formation affects both men and women equally, with the highest incidence occurring between the ages of 20 and 30.
In this article, we shall look at the pathophysiology, clinical features and management of keloid scarring.
In normal wound healing, there is a balance between new tissue biosynthesis and tissue degradation. This is achieved through the processes of apoptosis and remodelling of the extracellular matrix (ECM).
During keloid formation, there is a prolonged inflammatory phase (due to immune cell infiltration into the scar tissue). This contributes to excess fibroblast activity and increased deposition of ECM, resulting in the tissue projecting beyond the original wound margin.
The major risk factors for keloid formation are:
- Ethnicity – most common in Black and Asian populations.
- Age – the highest incidence occurring between 20-30yrs.
- Cause of injury – burns carry the highest risk.
- Anatomical site – most commonly occur in scars on the ear lobe, shoulders and sternal notch.
- Previous keloid formation
Aside from their characteristic visual appearance, keloids fortunately do not normally cause many other symptoms. A small proportion of patients may experience pain, itching, or burning in the scar tissue.
Keloid scars are raised above the skin around them and can take on the appearance of a dome-shape, extending beyond the original wound margin. They are often shiny and hairless, with varying consistency.
Early lesions are often erythematous, before becoming brownish and red, eventually turning pale as they age.
The Vancouver Scar Scale
The Vancouver Scar Scale can be used to quantify features of any scar, including keloids. It is particularly useful in monitoring the effectiveness of treatment.
It was initially designed for the assessment of burns, but has been found to be clinically useful in evaluating a wide range of scar types.
|2||Hyperpigmentation||Pink to Red||Yielding||2-5mm|
|4||Red to Purple||Banding|
The main differential diagnosis for a keloid scar is hypertrophic scarring – hyperprolific areas of scar tissue that keep within the confines of the wound margin. The main clinical features of each are compared in Table 1.
Other (rarer) diagnoses to consider are dermatofibroma or dermatofibrosarcoma protuberans.
|Hypertrophic Scars||Keloid Scars|
|Remain within the confines of the wound||Project beyond original wound margins|
|Usual regression over a period of time||Do not regress over time|
|Improves with surgical intervention||Outcomes worse with surgical intervention|
|Has no association with skin colour||Associated in individuals with a darker skin tone|
|Develops soon after injury||May develop several months after initial injury|
|Does not form spontaneously||May form spontaneously without prior injury|
|Develop in wound locations under high tension, such as shoulders, neck, knees and ankles||Occur anywhere on the body but predominately on earlobes, upper arms, sternal notch, and deltoids|
Table 1 – Comparison of hypertrophic and keloid scars.
Diagnosis is usually made on clinical findings, as described above. Biopsy of a lesion is rarely required.
A variety of management options are available for keloids.
Surgical excision of keloids is rarely performed. It has poor results, with recurrence rates between 40-100%. Surgical excision is thought to stimulate collagen synthesis – which results in the regrowth of a larger keloid.
There are a number of options for the treatment of keloids, which are typically more effective when used in combination with each other:
- Intralesional steroids are the most widely used treatment for keloids, acting as an anti-inflammatory agent that inhibits the fibroblast glucocorticoid receptors. This in turn downregulates the proliferation of fibroblasts and inhibits collagen synthesis.
- Silicone gel has also been shown to be an effective management. This can be either as a topical gel or as an elastic sheet (wrapped around the keloid scar for at least 12 hours per day).
- Radiation therapy reduces the recurrence of keloids, especially as an adjunct therapy. Naturally, radiation therapy runs the theoretical risk of inducing malignancy, which has limited its potential use.