When a scar is engrossed, it does not invade healthy tissue and lies across the normal 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 healthy tissue, then it is called a keloid scar. All kinds of scarring can appear 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 responses to damage. However, a keloid is an abnormal scar that grows beyond the limits of the original site of skin damage.

Keloids have the clinical appearance of an elevated amorphous growth and are frequently associated with pruritus and pain. Microscopy analysis reveals randomly organized collagen fibers in a hard 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 a widened or unattractive scar that does not grow 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. Like keloids, hypertrophic scars are associated with negative wound healing factors.

There are no particular characteristics that can reveal what will be the ultimate appearance of a scar or what kind 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 exaggerated scarring observed clinically that need different treatment approaches. The clinical signs and physical appearance define keloids and hypertrophic scars as separate lesions; however, they are often confused because of an apparent lack of morphologic differences. Nevertheless, medical differences between hypertrophic scarring and keloids have long been recognized by plastic surgeons and specialists. Yet, expressing these differences into morphologic or biochemical signs has created much conflict in the literature. This report is an attempt to clarify 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 represent chronic deforming dermatoses with a high resistance to therapy. The objective of our study was to assess 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 diseases. An item-pool was made modifying and supplementing the items of the Questionnaire on Experience with Skin Complaints. This questionnaire was distributed to 100 outpatients with keloids and hypertrophic scarring. A factor analysis was used to recognize the underlying dimensions. Two scales (psychological and physical deprivation) of the questionnaire with 9 and 5 items, respectively, were established. Test-retest validity of the questionnaire was excellent (corr>0.9). High validity was proposed 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 restriction of mobility (P less than 0.001). The psychological scale was associated with pain and restriction of mobility, although the relationships were lower. This study shows for the first time an impairment of quality of life in a large group of patients with keloid and hypertrophic scarring.