When a scar is engrossed, it doesn't invade normal tissue and lies across the relaxed skin tension lines (creases in the skin). This type of scar falls into the 'hypertrophic' category.

In the case that it is an elevated scar and invades normal tissue, then it is called a keloid scar. All types 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 uncommon reactions to trauma. However, a keloid is an aberrant scar that grows beyond the limits of the original site of skin injury.

Keloids have the clinical appearance of an elevated amorphous growth and are usually linked with pruritus and pain. Microscopy analysis shows randomly organized collagen fibers in a hard connective tissue matrix, making keloid removal a difficult task. In normal scars, the collagen bundles are disposed parallel to the skin surface.

A hypertrophic scar is a widened or unsightly scar that does not extend beyond the original limits of the wound. Unlike keloids, scars caused by hypertrophic actinic keratosis reach a certain size and subsequently stabilize or regress. Like keloids, hypertrophic scars are linked with adverse wound healing factors.

There are no certain signs that can indicate what will be the ultimate appearance of a scar or what type of scar it will be. The way in which a wound cures is different for every individual and is determined by genetics, 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 types of exaggerated scarring observed clinically that require different therapeutic approaches. The clinical course and physical appearance define keloids and hypertrophic scars as separate entities; however, they are usually confused because of an apparent lack of morphologic differences. Still, medical differences between hypertrophic scars and keloids have long been recognized by plastic surgeons and specialists. Yet, expressing these differences into morphologic or biochemical signs has prompted much conflict in the literature. This report is an attempt to explain the longstanding controversy regarding these 2 similar yet individual and nonidentical entities by highlighting 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 represent chronic deforming dermatoses with a strong resistance to therapy. The objective of our research was to assess for the first time the quality of life of people with hypertrophic scars and keloids, because they suffer from quality of life impairment as much as people with other chronic skin diseases. An item-pool was created modifying and supplementing the items of the Questionnaire on Experience with Skin Complaints. This questionnaire was given to one hundred outpatients with keloids and hypertrophic scars. A factor analysis was used to identify the underlying dimensions. Two scales (psychological and physical impairment) of the questionnaire with nine and five items, respectively, were used. Test-retest reliability of the questionnaire was excellent (corr>0.9). Good validity was suggested by the correlation of physical impairment with pain (P less or equal to 0.001), pruritus (P less than 0.001), and the proportion of impediment of mobility (P less than 0.001). The psychological scale was linked with pain and impediment of mobility, although the correlations were minor. This research demonstrates for the first time a deprivation of quality of life in a large group of sufferers with keloid and hypertrophic scars.