When a scar is thickened, it doesn't invade normal tissue and lies across the normal skin tension lines (creases in the skin). This kind of scar is referred to as hypertrophic.

In the case that it is a raised scar and invades normal tissue, then it is called a keloid scar. All kinds of scarring can occur on different areas of the body, but some areas like the chest, knees and elbows are more likely to scar.

Both keloid and hypertrophic scar tissues are atypical responses to trauma. However, a keloid is an abnormal scar that grows beyond the boundaries of the original site of skin injury.

Keloids have the clinical look of a raised amorphous growth and are usually linked with pruritus and pain. Microscopy observation shows randomly disposed collagen fibers in a dense connective tissue matrix, making keloid removal a difficult task. In normal scarring, the collagen bundles are disposed parallel to the skin surface.

A hypertrophic scar is an engrossed or unsightly scar that does not grow beyond the original boundaries of the wound. Unlike keloids, scars caused by hypertrophic actinic keratosis reach a certain size and then stabilize or regress. Similar to keloids, hypertrophic scars are linked with adverse wound healing factors.

There are no particular characteristics that can indicate what will be the ultimate look of a scar or what type of scar it will be. The way in which a wound heals is different for every person and is determined by genes, the environment and how you care for it.

Keloid or hypertrophic scar: A review of the literature

Atiyeh BS, Costagliola M, Hayek SN.

Division of Plastic and Reconstructive Surgery, American University of Beirut Medical Center, Beirut, Lebanon.

Keloid and hypertrophic scars are 2 kinds of exaggerated scarring observed clinically that need different therapeutic approaches. The clinical signs and physical look define keloids and hypertrophic scars as different lesions; however, they are often confused because of an apparent absence of morphologic differences. Still, clinical differences between hypertrophic scarring and keloids have long been recognized by plastic surgeons and dermatologists. Yet, translating these differences into morphologic or biochemical distinctions has prompted much conflict in the literature. This report is an attempt to explain the longstanding discussion involving these 2 similar yet individual and nonidentical entities by explaining the reported points of individualization as well as the similarities.

Quality of life of patients with keloid and hypertrophic scarring.

Bock O, Schmid-Ott G, Malewski P, Mrowietz U.

Primary Health Care Center, Halsan 2, Fabriksgatan 17, 55 185, Jonkoping, Sweden.

Keloid and hypertrophic scarring are chronic deforming dermatoses with a high resistance to treatment. The aim of our research was to evaluate for the first time the quality of life of patients with hypertrophic scarring and keloids, because they suffer from quality of life deprivation as much as patients with other chronic skin ailments. An item-pool was made changing and supplementing the items of the Questionnaire on Experience with Skin Complaints. This questionnaire was distributed to one hundred outpatients with keloids and hypertrophic scarring. A factor analysis was used to identify the underlying dimensions. Two scales (psychological and physical deprivation) of the questionnaire with 9 and 5 items, respectively, were used. Test-retest reliability of the questionnaire was excellent (corr>0.9). Good validity was suggested by the correlation of physical deprivation with pain (P less or equal to 0.001), pruritus (P less than 0.001), and the amount of restriction of mobility (P less than 0.001). The psychological scale was linked with pain and restriction of mobility, although the relationships were lower. This research demonstrates for the first time an impairment of quality of life in a large group of patients with keloid and hypertrophic scars.

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