Editing Scar (section)

== Types ==
[[File:Novak 7 (5451438566).jpg|thumb|right|Man with visible facial scars]]
All scarring is composed of the same collagen as the tissue it has replaced, but the composition of the scar tissue, compared to the normal tissue, is different.<ref name=collagenskinscar2010-08-20/> Scar tissue also lacks elasticity<ref name=elasticFibersScars>{{cite book | last = A. Bernard Ackerman, MD, Almut Böer, MD, Bruce Bennin, MD, Geoffrey J. Gottlieb, MD | title = Histologic Diagnosis of Inflammatory Skin Diseases An Algorithmic Method Based on Pattern Analysis: Embryologic, Histologic, and Anatomic Aspects: Elastic Fibers | publisher = Ardor Scribendi | edition = Third | date = January 2005 | pages = 522 | language = en | url = https://www.derm101.com/inflammatory/embryologic-histologic-and-anatomic-aspects/elastic-fibers/ | isbn = 9781893357259 | access-date = 19 September 2017 | archive-date = 20 June 2018 | archive-url = https://web.archive.org/web/20180620024213/https://www.derm101.com/inflammatory/embryologic-histologic-and-anatomic-aspects/elastic-fibers/ | url-status = dead }}</ref> unlike normal tissue which distributes [[Elastic fiber#Distribution|fiber elasticity]]. Scars differ in the amounts of collagen overexpressed. Labels have been applied to the differences in overexpression. Two of the most common types are [[Hypertrophic scar|hypertrophic]] and [[keloid]] scarring,<ref name=Roseborough2004/> both of which experience excessive stiff collagen bundled growth overextending the tissue, blocking off regeneration of tissues. Another form is atrophic scarring (sunken scarring), which also has an overexpression of collagen blocking regeneration. This scar type is sunken, because the collagen bundles do not overextend the tissue. [[Stretch marks]] (striae) are regarded as scars by some.

High [[melanin]] levels and either African or Asian ancestry may make adverse scarring more noticeable.<ref>{{cite journal |doi=10.1016/j.sder.2009.04.002 |pmid=19608056 |title=Update on the Management of Keloids |journal=Seminars in Cutaneous Medicine and Surgery |volume=28 |issue=2 |pages=71–76 |year=2009 |last1=Kelly |first1=A. Paul |doi-broken-date=1 November 2024 }}</ref>

=== Hypertrophic ===
{{main|Hypertrophic scars}}
[[Hypertrophic scars]] occur when the body overproduces [[collagen]], which causes the scar to be raised above the surrounding skin. [[Organ hypertrophy|Hypertrophic]] scars take the form of a red raised lump on the skin for lighter pigmented skin and the form of dark brown for darker pigmented skin. They usually occur within 4 to 8 weeks following wound infection or wound closure with excess tension and/or other traumatic skin injuries.<ref name=Roseborough2004>{{cite journal |doi=10.2119/molmed.2009.00153 |pmid=20927486 |pmc=3022978 |year=2011 |last1=Gauglitz |first1=Gerd |journal=Molecular Medicine |volume=17 |issue=1–2 |pages=113–25 |last2=Korting |first2=Hans |title=Hypertrophic Scarring and Keloids: Pathomechanisms and Current and Emerging Treatment Strategies }}</ref>

===Keloid===
{{Main|Keloid}}
Keloid scars are a more serious form of excessive scarring, because they can grow indefinitely into large, tumorous (although benign) [[neoplasm]]s.<ref name=Roseborough2004/>

Hypertrophic scars are often distinguished from keloid scars by their lack of growth outside the original wound area, but this commonly taught distinction can lead to confusion.<ref name="Roseborough2004a">{{cite journal |vauthors=Roseborough IE, Grevious MA, Lee RC | title = Prevention and treatment of excessive dermal scarring | journal = J Natl Med Assoc | volume = 96 | issue = 1 | pages = 108–16 | date = January 2004 | pmid = 14746360 | pmc = 2594768 }}</ref>

Keloid scars can occur on anyone, but they are most common in dark-skinned people.<ref>Martini, Frederic H. (2006). ''Fundamentals of Anatomy & Physiology,'' Seventh Edition, p. 171. Benjamin Cummings, San Francisco.</ref> They can be caused by surgery, cuts, accident, [[Acne vulgaris|acne]] or, sometimes, [[body piercings]]. In some people, keloid scars form spontaneously. Although they can be a cosmetic problem, keloid scars are only inert masses of collagen and therefore completely harmless and not cancerous. However, they can be itchy or painful in some individuals. They tend to be most common on the [[shoulder]]s and [[chest]]. Hypertrophic scars and keloids tend to be more common in wounds closed by secondary intention.<ref name=secinten201104/> Surgical removal of keloid is risky and may exacerbate the condition and worsening of the keloid.

=== Atrophic ===
[[File:Atrophic scar of Ehlers Danlos syndrome.jpg|thumb|Atrophic "cigarette paper" scar in Ehlers–Danlos patient]]
An atrophic scar takes the form of a sunken recess in the skin, which has a pitted appearance. These are caused when underlying structures supporting the skin, such as [[fat]] or [[muscle]], are lost. This type of scarring is often associated with acne,<ref>{{cite journal | author = Goodman GJ | title = Postacne scarring: A review of its pathophysiology and treatment | journal = Dermatologic Surgery | volume = 26 | issue = 9 | pages = 857–871 | year = 2000 | pmid = 10971560 | doi=10.1046/j.1524-4725.2000.99232.x| s2cid = 25244676 }}</ref><ref>{{cite journal |vauthors=Fabbrocini G, Annunziata MC, D'Arco V, De Vita V, Lodi G, Mauriello MC, Pastore F, Monfrecola G | title = Acne Scars: Pathogenesis, Classification and Treatment | journal = Dermatology Research and Practice | volume = 2010 | pages = 1–13 | year = 2010 | pmid = 20981308 | pmc = 2958495 | doi = 10.1155/2010/893080 | doi-access = free }}</ref> [[chickenpox]], other diseases (especially ''[[Staphylococcus]]'' infection), surgery, certain insect and spider bites, or accidents. It can also be caused by a genetic [[connective tissue]] disorder, such as [[Ehlers–Danlos syndrome]].<ref>{{Cite web|url=http://www.uptodate.com/contents/clinical-manifestations-and-diagnosis-of-ehlers-danlos-syndromes#H35121407|title=Clinical manifestations and diagnosis of Ehlers-Danlos syndromes|website=www.uptodate.com|access-date=2017-06-15}}</ref>

=== Stretch marks ===
{{Main|Stretch marks}}
Stretch marks (technically called ''striae'') are also a form of scarring. These are caused when the skin is stretched rapidly (for instance during [[pregnancy]],<ref name=":0">{{Cite journal |last1=Brennan |first1=Miriam |last2=Young |first2=Gavin |last3=Devane |first3=Declan |date=2012-11-14 |title=Topical preparations for preventing stretch marks in pregnancy |journal=The Cochrane Database of Systematic Reviews |volume=2012 |issue=11 |pages=CD000066 |doi=10.1002/14651858.CD000066.pub2 |issn=1469-493X |pmid=23152199|pmc=10001689 }}</ref> significant [[weight gain]], or adolescent [[growth spurt]]s),<ref>{{cite journal |vauthors=Elsaie ML, Baumann LS, Elsaaiee LT | title = Striae Distensae (Stretch Marks) and Different Modalities of Therapy: An Update | journal = Dermatologic Surgery | volume = 35 | issue = 4 | pages = 563–573 | year = 2009 | pmid = 19400881 | doi = 10.1111/j.1524-4725.2009.01094.x | s2cid = 7887237 }}</ref> or when skin is put under tension during the healing process (usually near [[joints]]). This type of scar usually improves in appearance after a few years.<ref name=":0" />

Elevated [[corticosteroid]] levels are implicated in striae development.<ref>{{cite journal |vauthors=Hengge UR, Ruzicka T, Schwartz RA, Cork MJ | title = Adverse effects of topical glucocorticosteroids | journal = Journal of the American Academy of Dermatology | volume = 54 | issue = 1 | pages = 1–15 | year = 2006 | pmid = 16384751 | doi = 10.1016/j.jaad.2005.01.010 }}</ref>

=== Umbilical ===
Humans and other [[placental mammal]]s have an umbilical scar (commonly referred to as a [[navel]]) which starts to heal when the [[umbilical cord]] is cut after birth. Egg-laying animals have an umbilical scar which, depending on the species, may remain visible for life or disappear within a few days after birth.<ref>{{cite news|url=https://www.smithsonianmag.com/arts-culture/what-types-of-animals-have-been-to-space-and-more-questions-from-our-readers-63029589/ |title=What Types of Animals Have Been to Space and More Questions From our Readers|work= Smithsonian |date=May 2012|access-date=25 November 2017}}</ref><ref>{{cite web|url=https://www.fws.gov/southwest/es/arizona/Documents/Redbook/Flat-Tailed%20Horned%20Lizard%20RB.pdf |title=Flat-tailed horned lizard (Phrynosoma mcallii)|website= US Fish & Wildlife Service |access-date=25 November 2017}}</ref>