Keloid, also known as keloid disorder and keloidal scar, is the formation of a type of scar which, depending on its maturity, is composed mainly of either type III (early) or type I (late) collagen. It is a result of an overgrowth of granulation tissue (collagen type III) at the site of a healed skin injury, which is then slowly replaced by collagen type I. Keloids are firm, rubbery lesions or shiny, fibrous nodules, and can vary from pink to the color of the person's skin or red to dark brown. A keloid scar is benign and not contagious, but sometimes accompanied by severe itchiness, pain, and changes in texture. In severe cases, it can affect the movement of the skin. In the United States, keloid scars are seen 15 times more frequently in people of sub-Saharan African descent than in people of European descent. There is a higher tendency to develop a keloid among those with a family history of keloids and people between the ages of 10 and 30 years. Keloids should not be confused with hypertrophic scars, which are raised scars that do not grow beyond the boundaries of the original wound.
Signs and symptoms
Keloids expand in claw-like growths over normal skin. They can hurt with a needle-like pain or to itch, the degree of sensation varying from person to person. Keloids typically form within scar tissue. Collagen, used in wound repair, tends to overgrow in this area, sometimes producing a lump many times larger than that of the original scar. They can also range in color from pink to red. Although they usually occur at the site of an injury, keloids can also arise spontaneously. They can occur at the site of a piercing and even from something as simple as a pimple or scratch. They can occur as a result of severe acne or chickenpox scarring, infection at a wound site, repeated trauma to an area, excessive skin tension during wound closure or a foreign body in a wound. Keloids can sometimes be sensitive to chlorine. If a keloid appears when someone is still growing, the keloid can continue to grow as well.
Location Keloids can develop in any place where skin trauma has occurred. They can be the result of pimples, insect bites, scratching, burns, or other skin injuries. Keloid scars can develop after surgery. They are more common in some sites, such as the central chest (from a sternotomy), the back and shoulders (usually resulting from acne), and the ear lobes (from ear piercings). They can also occur on body piercings. The most common spots are the earlobes, arms, pelvic region, and over the collarbone.
Cause Most skin injury types can contribute to scarring. This includes burns, acne scars, chickenpox scars, ear piercing, scratches, surgical incisions, and vaccination sites. According to the US National Center for Biotechnology Information, keloid scarring is common in young people between the ages of 10 and 20. Studies have shown that those with darker complexions are at a higher risk of keloid scarring as a result of skin trauma. They occur in 15–20% of individuals with sub-Saharan African, Asian, or Latino ancestry, significantly less in those of a Caucasian background. Although it was previously believed that people with albinism did not get keloids, a recent report described the incidence of keloids in Africans with albinism. Keloids tend to have a genetic component, which means one is more likely to have keloids if one or both of their parents have them. No single gene has yet been identified as a causing factor in keloid scarring, although several susceptibility loci have been discovered, most notably in Chromosome 15.
Genetics
People who have ancestry from Sub-Saharan Africa, Asia, or Latin America are more likely to develop a keloid. Among ethnic Chinese in Asia, the keloid is the most common skin condition. In the United States, keloids are more common in African Americans and Hispanic Americans than European Americans. Those who have a family history of keloids are also susceptible since about 1/3 of people who get keloids have a first-degree blood relative (mother, father, sister, brother, or child) who also gets keloids. This family trait is most common in people of African and/or Asian descent. The development of keloids among twins also lends credibility to the existence of a genetic susceptibility to develop keloids. Marneros et al. (1) reported four sets of identical twins with keloids; Ramakrishnan et al. also described a pair of twins who developed keloids at the same time after vaccination. Case series have reported clinically severe forms of keloids in individuals with positive family history and black African ethnic origin.
Pathology
Histologically, keloids are fibrotic tumors characterized by a collection of atypical fibroblasts with excessive deposition of extracellular matrix components, especially collagen, fibronectin, elastin, and proteoglycans. Generally, they contain relatively acellular centers and thick, abundant collagen bundles that form nodules in the deep dermal portion of the lesion. Keloids present a therapeutic challenge that must be addressed, as these lesions can cause significant pain, pruritus (itching), and physical disfigurement. They may not improve in appearance over time and can limit mobility if located over a joint. Keloids affect all sexes equally, although the incidence in young female patients has been reported to be higher than in young males, probably reflecting the greater frequency of earlobe piercing among women. The frequency of occurrence is 15 times higher in highly pigmented people. People of African descent have an increased risk of keloid occurrences.
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