When a scar is thickened, it does not invade healthy tissue and lies across the relaxed 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 healthy tissue, then it is called a keloid scar. All kinds of scarring can occur on different areas of the body, but some areas such as the chest, knees and elbows are more likely to scar.

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

Keloids have the clinical look of a raised amorphous growth and are frequently associated with pruritus and pain. Microscopy observation reveals randomly organized collagen fibers in a hard connective tissue matrix, making keloid removal a difficult task. In normal scars, the collagen bundles are arranged parallel to the skin surface.

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

There are no particular characteristics that can reveal what will be the ultimate look 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 two kinds of excessive scarring observed clinically that need different therapeutic approaches. The clinical course and physical look define keloids and hypertrophic scars as different entities; however, they are often confused because of an apparent absence 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 distinctions has created much conflict in the literature. This report is an attempt to explain the longstanding controversy involving these 2 similar yet separate and nonidentical entities by highlighting the reported points of differentiation 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 high resistance to therapy. The aim of our research was to evaluate for the first time the quality of life of people with hypertrophic scars and keloids, because they suffer from quality of life deprivation as much as people with other chronic skin ailments. An item-pool was created modifying and complementing the items of the Questionnaire on Experience with Skin Complaints. This questionnaire was distributed to 100 outpatients with keloids and hypertrophic scars. A factor analysis was used to identify the underlying dimensions. Two scales (psychological and physical deprivation) of the questionnaire with nine and five items, respectively, were used. Test-retest reliability of the questionnaire was optimal (corr>0.9). High 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 proportion of impediment of mobility (P less than 0.001). The psychological scale was associated with pain and impediment of mobility, although the correlations were minor. This research shows for the first time a deprivation of quality of life in a large group of sufferers with keloid and hypertrophic scarring.