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Definition:
Keloid: An exuberant scar caused by excessive deposition of collagen that spreads beyond the edges of the site of injury. Some keloids occur spontaneously.
Hypertrophic Scar: An exuberznt scar caused by excessive deposition of collagen but remains limited within the edges of the site of injury. These always follow an injury.
Types of Keloids:
Post-traumatic: These keloids occur int he scar that forms following any type of injury, which causes significant inflammation in the skin. The injury might be a surgical incision, an accidental cut, a pierced ear,
deep cystic acne, an abrasion caused by a fall, etc.
Spontaneous: Some keloids seem to occur spontaneously. Many individuals develop keloids on the chest. It is possible that the person has acne underlying the “spontaneous” keloid.
Syndromal: Individuals with Rubinstein-Taybi are in this group.
Who Gets Keloids?
Group1: Many individuals of African, Polynesian and South Pacific ancestry have a propensity to developing keloids and/or hypertrophic scars. This tendency can be mild to “big scars” to extreme where slight
injuries produce severe large, almost incapacitating scars that are exceedingly resistant to all forms of therapy. Group 2: Some individuals with disorders like the RTS have a propensity to develop keloids. In the Netherlands the prevalence among the RTS group is 22%.
Group 3: Although these individuals are not in the human species, they develop excessive scarring. A breed of mice called the “tight skin” mouse has such a disease. Their significance is
that they are a model to study the process of collagen formation and its regulation.
What Causes Keloids and Hypertrophic Scars?
- The actual cause is not known although much work is being done on wound healing and the role of cytokines in control of collagen formation. This type of research might provide clues to the cause and treatment in the
next few years.
- Cells: There are two types of white blood cells or inflammatory cells - nmast cells and eosinophils - both of which have been implicated in keloids or excessive collagen production. Their actual role is not known.
- Cytokines: Cytokines are proteins much like the hormone insulin. They can affect the cell that makes them (an autocrine effect); adjacent cells (paracine effect); or distal cells (endocrine effect). Cytokines
are known to control many cellular functions. During wound healing, many different cytokines are released, some early in the healing process (first few days); other late (first few weeks); and some are detectable only
late in the healing process (a month or later). No one cytokine is found at any given time but a group. Healing with cytokines is like an orchestra with different instruments playing at different intensities at
specific times during the musical process.
- Some specific cytokines that could be involved are TGF-b, PDGF, the interferons, prostaglandins (not actually proteins), interleukin-6, tumor necrosis factor (the name does not reflect function), interleukin-2 and
others. The actual role of any cytokine in formation of keloids is not known.
Treatment of Keloids and Hypertropnhic Scars:
- Steroids: The most traditional treatment is intralesional injections of cortisones like Kenalog, usually 10 mg/ml. This treatment sometimes is useful, especially in hypertrophic scars.
- Combination Therapy: Cortisones combined with surgical excision, X-ray of the wound, laser ablation of the wound, or all of the above. Usually these more agrgressive therapies are used in patients with exreme
keloids and tend not to be worthwhile.
- Silicone splints: The burn surgeons have observed the scarring which follows skin grafting is minimized by pressure. Silicone splints applied under gentle pressure for months have been reported to diminish the size of
keloids or more often hypertrophic scars.
- Injections of interferon: Interferon-a has been reported to be useful in treating keloids. It must be done frequently, 3x per/week and for some months. Inferon causes significant side effects like fever,
myalgias, and other flu-like symptoms. It is also expensive. Like the other therapies it is far from a panacea for keloids or hypertrophic scars.
The cure for keloids or their prevention is not yet available.
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