Keloids are overgrowths of scar tissue that go beyond the boundaries of the original skin injury. They can develop after any skin trauma, such as acne, body piercings, burns, chickenpox, cuts, insect bites, scratches, surgical incisions, vaccinations, and wounds. Keloids tend to be more common in certain skin types and ethnicities.
What are keloids?
Keloids are fibroproliferative disorders of wound healing in which excessive collagen is deposited at the site of cutaneous injury. They are firm, rubbery lesions or shiny, fibrous nodules that vary in size, shape, and color. Keloids grow beyond the borders of the original wound and do not regress spontaneously over time.
Keloids can range from pink to red to dark brown in color. They often have a smooth, nodular surface and a rubbery or firm texture. Keloids cause symptoms such as pain, itching, and a burning sensation. They may restrict movement if they form over a joint.
Keloids form due to an overgrowth of granulation tissue (collagen type 3) that extends beyond the borders of a wound. They contain large, thick collagen bundles and an abundance of GAGs, especially chondroitin sulfate. Keloids arise from fibroblasts and keratinocytes that have escaped normal control mechanisms of wound healing.
What causes keloids?
The exact cause of keloids is unknown, but they appear to have a genetic component. Keloids form when skin is injured and the cells that make scar tissue (fibroblasts) overproduce collagen as part of the healing process. This overproduction leads to the extra scar tissue that builds up to form a keloid.
Factors that increase the risk of developing keloids include:
- Genetics – Keloids tend to run in families. Having a family member with keloids increases your risk.
- Age – Keloids are more common in younger people, ages 10 to 30.
- Sex – Keloids are more common in females.
- Race – Darker skinned individuals, such as African Americans, Hispanics, and Asians, are at increased risk.
- Skin injury – Any type of skin trauma can trigger keloids, from acne to body piercings, burns, cuts, scratches, surgery, tattoos, and vaccine injections.
- Skin tension – Areas with high skin tension, like the chest, shoulders, earlobes, and cheeks, are more prone to keloids.
- Inflammation – Chronic inflammation may promote keloid growth.
- Hormones – Hormonal changes during puberty and pregnancy may exacerbate keloids.
In susceptible individuals, the fibroblasts produce excessive collagen after skin injury, leading to keloid overgrowth. Genetic mutations, immune system abnormalities, and altered apoptotic pathways in keloid tissue may contribute to unchecked fibroblast activity and collagen accumulation.
What skin types and ethnicities are prone to keloids?
Keloids tend to occur more frequently in certain skin types and ethnic groups, including:
- African Americans – Keloids develop in 4.5% to 16% of African Americans. The prevalence is 15 times higher than in Caucasians.
- Hispanics – Hispanics have an increased tendency to form keloids.
- Asians – Keloids occur in Asians at a rate of 4-10 times higher than Caucasians.
People with darker skin tones have higher risk due to increased susceptibility of melanocytes (pigment producing cells) to inflammation. Darker skinned individuals are also more prone to raised scars and contain higher numbers of fibroblasts in their skin.
Additional factors that contribute to increased keloid risk in these groups include:
- Higher skin tension in certain ethnic groups
- Cultural practices like piercings and branding
- Genetic predisposition
Keloids occur less frequently in fair skinned individuals, like those of Caucasian and Northern European descent, but can still develop in susceptible individuals after skin injury.
What skin sites tend to form keloids?
Keloids commonly develop on skin sites with increased tension, which include:
- Chest
- Shoulders
- Earlobes
- Upper back
- Cheeks
- Chin
- Neck
- Thighs
- Upper arms
These areas experience high mechanical stress from muscle and skin tension, making them more prone to keloid growth. Stretched skin at the site of injury signals to fibroblasts to produce more collagen during wound healing.
Keloids also frequently arise from ear piercings, particularly in the cartilage of the upper ear. Other common sites are the shoulders and chest from acne lesions or chickenpox scars. Surgical sites, like the sternum after open heart surgery, often develop keloids due to deep tissue trauma.
Facial keloids
The face contains areas of high skin tension, making it susceptible to keloids after injury. Common facial sites include:
- Earlobes
- Jawline
- Cheeks
- Chin
- Forehead
- Nostrils
Facial keloids may arise after acne, trauma from injury or surgery, body piercings, chickenpox scars, and laser resurfacing procedures. They can cause significant cosmetic concerns.
Body keloid locations
Keloids on the body often form at the following sites:
- Chest
- Shoulders
- Upper back
- Sternum
- Ear cartilage
- Thighs
- Upper arms
- Abdomen
- Groin
- Knees
They can develop after surgical procedures, acne lesions, body piercings, chickenpox scars, trauma from injury, tattoos, and vaccinations.
Conclusion
In summary, keloids are overgrown scars that are more prevalent among African Americans, Hispanics, and Asians. They frequently arise at skin sites experiencing high tension, like the chest, shoulders, earlobes, upper back, and cheeks. Individuals who are under age 30, female, or have a family history also have increased susceptibility. All skin types can form keloids, but the risk varies between ethnic groups. Knowing your predisposition can help guide preventative care after skin injuries to avoid excessive scarring.