What are Keloids?
Keloids are a type of raised scar that grows beyond the boundaries of the original skin injury. They are firm, rubbery lesions or shiny, fibrous nodules that can vary from pink to flesh-colored or red to dark brown in color. Keloids occur when the body overproduces collagen while healing from a wound, forming an excessive amount of scar tissue at the site of the injury.
Some key facts about keloids:
– Keloids can form after any type of skin trauma, including cuts, burns, acne, insect bites, tattoos, piercings, surgery, or vaccinations. They are more common on the upper chest, shoulders, earlobes, and cheeks.
– Keloids tend to run in families, so genetics may play a role. They are more common in people with darker skin tones.
– They can range in size from very small to very large. Some keloids expand to cover a large region of skin over time.
– Keloids may be itchy, painful, or cause a burning sensation. They do not usually regress over time without treatment.
– Keloids are benign (noncancerous) skin growths, but can cause functional impariment and psychological distress.
Why Do Keloids Expand Over Time?
There are several reasons why keloids tend to progressively enlarge after they first form:
– Chronic inflammation – Keloids have ongoing inflammation within the lesion and the surrounding tissue. Inflammatory cells produce growth factors that stimulate collagen production. This results in continued scar proliferation.
– Abnormal fibroblast activity – Fibroblasts are cells that produce collagen and other extracellular matrix proteins during wound healing. In keloids, fibroblasts become hyperactive and deposit excessive amounts of collagen into the scar tissue.
– Tension on the scar – Skin tension at the wound site encourages keloid growth. The stretching of the skin triggers more collagen synthesis by fibroblasts. Keloids that form over joint surfaces and the chest are chronically exposed to tension forces.
– Reinjury or irritation – Further injury, trauma, or irritation to a keloid can trigger more scar enlargement. Things like clothing friction, scratching, piercings, surgery, and skin infections can stimulate growth.
– Hormonal factors – Hormonal changes associated with puberty, pregnancy, and menopause may cause fluctuations in keloid size. Estrogen is believed to influence fibrosis and collagen production.
– Genetic factors – Certain genetic mutations involved in wound healing and collagen regulation are linked to enhanced keloid growth. The familial inheritance of keloids also points to genetic contributors.
– Biochemical imbalance – Keloids have lower levels of the protein collagenase, which breaks down collagen, and higher levels of proteins that promote collagen accumulation. This imbalance promotes extracellular matrix accumulation.
What Makes Keloids Different Than Normal Scars?
Keloids form much more scar tissue than is needed for normal wound healing. Here are some key differences between keloids and regular scars:
| Keloids | Normal Scars |
|---|---|
| – Grow larger than the original wound | – Remain within boundaries of the original wound |
| – Continue to grow over time | – Do not grow significantly after initially forming |
| – Do not regress spontaneously | – Often improve in appearance 1-2 years after injury |
| – Consist of randomly arranged collagen fibers | – Have organized, parallel bundles of collagen |
| – Can have nodular, shiny, irregular texture | – Are flat, thinner, and more uniform |
| – Tend to be red, dark, or hyperpigmented | – Are paler than surrounding normal skin |
| – Persist for years without treatment | – Mature and stabilize over months |
These differences reflect the fact that keloid fibroblasts overproduce disorganized scar tissue components compared to normal wound healing. The tendency of keloids to aggressively expand differentiates them from hypertrophic scars, which remain within injury margins.
What Causes Keloids to Initially Form?
Keloids arise from a combination of genetic, physiologic, and environmental factors that alter the skin’s wound healing response:
– Family history – Keloids have a strong hereditary link, indicating certain genetic mutations promote excessive scarring. Variants affecting wound healing proteins have been identified.
– Darker skin pigmentation – Individuals with darker skin tones have a 15 times higher risk of getting keloids. Racial differences in collagen turnover and sebum production may contribute.
– Younger age – Keloids are more common in those under 30 years old. The activity of fibroblasts declines with aging.
– Skin tension – Areas like the chest and shoulders experience high mechanical tension that spurs collagen synthesis during wound repair. This can lead to overabundant scarring.
– Severe injury – Larger wounds that deeply damage the skin and subcutaneous tissue provide triggers for excessive extracellular matrix deposition by fibroblasts and myofibroblasts.
– Delayed wound closure – Slow healing wounds with ongoing inflammation are linked to increased keloid formation compared to rapidly closing wounds.
– Foreign body reaction – Items embedded in the skin like splinters, piercing jewelry, sutures, and shrapnel can cause irritation that provokes abnormal scarring.
– Hormones – Estrogen, progesterone, and androgens influence fibroblast gene expression and may enhance keloid development at puberty, pregnancy and menopause.
– Infection – Bacterial, viral, and fungal infections cause inflammation that can trigger keloid generation in susceptible individuals.
How Do Keloids Enlarge Over Time?
The progressive enlargement of keloids occurs due to both continued collagen deposition within the scar tissue and lateral expansion beyond original wound boundaries:
– Fibroblasts and myofibroblasts embedded within keloids maintain an activated state that drives further collagen production and secretion of extracellular matrix proteins like fibronectin and elastin. This generates new scar tissue that thickens the keloid nodule over time.
– Enzymes like lysyl oxidase crosslink collagen fibers in the keloid, increasing tissue tensile strength and stiffness. This provides force resistance that allows vertical scar expansion when pressed against adjacent normal skin.
– Proteoglycans like versican bind water and hydrate the keloid, enabling maintenance of turgor pressure that contributes to lesion growth.
– The keloid lesion extends outward, beyond the initial injury site, due to traction forces from contracted myofibroblasts, pressure caused by swelling, and the enlarged scar tissue pushing against the surrounding skin.
– Ongoing low levels of chronic inflammation, collagenase inhibition, and decreased collagen breakdown allow keloids to continuously accumulate scar tissue components rather than resolving.
– Reinjury, friction, scratching, and skin tension provide external stimuli that further stimulate fibroblast activity and collagen synthesis to expand keloids horizontally across the skin surface.
Factors That Can Cause Keloids to Expand
Certain influences can increase the likelihood that a keloid scar will progressively enlarge:
Skin Tension
– High tension areas like the chest, shoulders, upper back, and neck make keloids more prone to lateral growth. Tension triggers fibroblasts to produce more collagen.
Trauma or Reinjury
– Additional injury, piercing, scratching, surgery, or friction to the site of a keloid reactivates wound healing processes that stimulate growth.
Infection
– Bacterial, fungal, or viral infection causes inflammation and cytokine release that activates fibroblasts and collagen production.
Hormone Fluctuations
– Puberty, menstruation, pregnancy, and menopause involve shifts in estrogen, progesterone, testosterone and growth factors that may impact keloid fibrosis.
Tanning and Sun Exposure
– UV radiation can darken keloids and potentially damage skin adjacent to the keloid, instigating lateral expansion.
Genetic Predisposition
– Variants in genes involved in wound healing, inflammation, and collagen regulation increase susceptibility to unchecked keloid enlargement.
Young Age
– Keloids are more active and likely to expand in those who are younger, when fibroblast activity is highest.
Ethnicity
– Darker skin types have a higher risk for keloids that progress. Racial differences in collagen turnover may be a factor.
Delayed Wound Closure
– Slow healing wounds with ongoing inflammation have higher odds of forming widely enlarging keloids.
The Impact of Keloid Size on Symptoms
As keloids enlarge, they can cause worsening aesthetic and functional problems:
Mild Keloids
– Small keloids may be asymptomatic or mildly itchy/painful
– Minimal impact on range of motion if located over a joint
– Can often be covered by clothing; limited psychosocial effects
Moderate Keloids
– Can cause pulling, rubing and irritation with clothing or jewelry
– Restriction of movement if located over joint creases
– May cause significant pruritis and soreness
– Visible and difficult to cover; moderate body image issues
Severe Keloids
– Very painful lesions with severe pruritis
– Can restrict joint mobility if extensive
– Can limit ability to wear clothing, glasses, or jewelry
– Highly disfiguring; major psychosocial distress
– Earlobe keloids may distort the shape of the ear or cause hearing loss
Larger keloids tend to be symptomatic and are perceived as more unsightly. Giant keloids that are very extensive can severely limit function and mobility while drastically altering appearance.
Treatments to Stop Keloid Growth
A range of therapies are available to impede the spread of expanding keloids:
Corticosteroid Injections
– Steroids like triamcinolone or Kenalog injected directly into keloids can reduce inflammation and inhibit fibroblast proliferation and collagen synthesis.
Cryotherapy
– Freezing keloids with liquid nitrogen induces cell death and slows growth by damaging fibroblasts and reducing blood supply.
Laser Therapy
– Ablative and non-ablative lasers generate heat to shrink keloids by promoting collagen remodeling and apoptosis of fibroblasts and inflammatory cells.
Radiation
– Targeted radiation generates free radicals that damage hyperactive fibroblasts, slowing collagen production and lesion growth.
Silicone Gel Sheeting
– Silicone sheets likely work by hydrating scar tissue, limiting collagen cross-linking, and softening keloids to restrain enlargement.
Surgery
– Excision of the keloid followed by radiation, steroid injections, or pressure dressings helps control regrowth of the scar post-operatively.
Compression Therapy
– Compressive garments or bandages apply pressure to flatten keloids and limit expansion by inhibiting blood flow.
What Causes Keloids to Stop Growing?
In some cases, keloids may halt their enlargement due to certain changes:
– The keloid reaches maximal size based on the amount of available skin surface area. Extensive keloids cannot continue growing outward indefinitely.
– The underlying trauma or inflammation that incited the keloid is resolved. This removes stimuli driving continued collagen production.
– Collagenase activity increases, enabling collagen breakdown to catch up with new deposition. This prevents further accumulation.
– Fibroblast activity diminishes over time. Fibroblasts have a finite lifespan in wound tissue of around 2-4 months.
– With aging, steroid levels, growth factors, and fibroblast metabolism decrease. This slows new scar formation.
– Successful treatment with steroids, surgery, radiation, or other therapies permanently inactivates the pathogenic fibroblasts.
– Environmental irritants like friction or infection are eliminated. This prevents reactivation of the wound healing cascade.
– Nutritional deficiencies develop, depriving fibroblasts of amino acids needed for protein synthesis.
– The genes promoting fibrosis become silenced, halting overexpression of collagen and extracellular matrix proteins.
– Normal regulatory mechanisms that restrain scarring like apoptosis kick back in to control keloid fibroblasts.
Preventing the Recurrence and Spread of Keloids
Once a keloid stops growing, measures can be implemented to reduce the likelihood it will enlarge again or form expanding keloids elsewhere:
– Avoid unnecessary trauma, piercings, elective surgery, and sunburns to areas prone to keloids.
– Treat wounds at risk for keloids with silicone gel sheets or pressure dressings to minimize scarring.
– After keloid surgery, use radiation, steroid injections, and compression for 8-12 weeks to prevent recurrence.
– Apply silicone gel sheeting or topical drugs like onions extract regularly to elicit collagen breakdown.
– Taking preventive action before and during puberty, pregnancy, and menopause may limit hormone-driven expansion.
– Manage any skin infections quickly and keep keloids clean to prevent microbial-driven inflammation.
– Wear loose clothing and padding to protect keloids from friction and skin tension forces.
– Apply moisturizer daily to keep skin hydrated, supple, and deter minor injuries.
– Avoid picking, scratching or otherwise irritating existing keloids to prevent re-stimulation of wound healing.
– Seek genetic counseling if there is a strong family history of progressive keloids.
Conclusion
Keloids become larger lesions over time due to intrinsic factors like genetics, hormone changes, and an imbalance between collagen synthesis and degradation. Extrinsic elements like skin tension, trauma, and infection also drive ongoing keloid expansion. Understanding the molecular factors that allow keloids to continuously grow provides insight on potential treatment strategies. Combination therapy targeting inflammation, fibroblast activity, and collagen accumulation shows promise to halt keloid enlargement. With a coordinated approach, it is possible to restrain the spread of disfiguring keloids.