Freckle - Wikipedia Freckle From Wikipedia, the free encyclopedia Jump to navigation Jump to search Clusters of concentrated melanin "Freckles" redirects here. For other uses, see Freckles (disambiguation). "Frickle" redirects here. For other uses, see Fried pickle. "Ephelis" redirects here. For the moth genus, see Ephelis (moth). This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed.Find sources: "Freckle" – news · newspapers · books · scholar · JSTOR (February 2022) (Learn how and when to remove this template message) Medical conditionFreckleOther namesEphelides, ephelisSlight facial freckles on a child.SpecialtyDermatology Freckles are clusters of concentrated melaninized cells which are most easily visible on people with a fair complexion. Freckles do not have an increased number of the melanin-producing cells, or melanocytes, but instead have melanocytes that overproduce melanin granules (melanosomes) changing the coloration of the outer skin cells (keratinocytes). As such, freckles are different from lentigines and moles,[1] which are caused by accumulation of melanocytes in a small area. Freckles can appear on all types of skin tones. Of the six Fitzpatrick skin types, they are most common on skin tones 1 and 2, which usually belong to North Europeans. However, it can also be found on people all over the world. Contents br 1 Biology 1.1 Genetics 2 Types 3 See also 4 References 5 External links Biology edit The formation of freckles is caused by exposure to sunlight. The exposure to UV-B radiation activates melanocytes to increase melanin production, which can cause freckles to become darker and more visible. This means that one who has never developed freckles may develop them suddenly following extended exposure to sunlight. Freckles are predominantly found on the face, although they may appear on any skin exposed to the sun, such as arms or shoulders. Heavily distributed concentrations of melanin may cause freckles to multiply and cover an entire area of skin, such as the face. Freckles are rare on infants, and more commonly found on children before puberty. Upon exposure to the sun, freckles will reappear if they have been altered with creams or lasers and not protected from the sun, but do fade with age in some cases. Freckles are not a skin disorder, but people with freckles generally have a lower concentration of photo-protective melanin, and are therefore more susceptible to the harmful effects of UV radiation. It is suggested that people whose skin tends to freckle should avoid overexposure to sun and use sunscreen.[2][3] Genetics edit Women with freckles The presence of freckles is related to rare alleles of the MC1R gene, though it does not differentiate whether an individual will have freckles if they have one or even two copies of this gene. Also, individuals with no copies of the MC1R do sometimes display freckles. Even so, individuals with a high number of freckling sites have one or more of variants of the MC1R gene. Of the variants of the MC1R gene Arg151Cys, Arg160Trp, and Asp294His are the most common in the freckled subjects.[4][5][6] The MC1R gene is also associated with red hair more strongly than with freckles. Most red-haired individuals have two variants of the MC1R gene and almost all have one.[5] The variants that cause red hair are the same that cause freckling.[4] Freckling can also be found in areas, such as Japan, where red hair is not seen. These individuals have the variant Val92Met which is also found in Europeans, although it has minimal effects on their pigmentation. The R162Q allele has a disputed involvement in freckling.[7] The variants of the MC1R gene that are linked with freckles started to emerge in the human genotype when humans started to leave Africa. The variant Val92Met arose somewhere between 250,000 and 100,000 years ago, long enough for this gene to be carried by humans into central Asia. Arg160Trp is estimated to have arisen around 80,000 years ago while Arg151Cys and Asp294His have been estimated to arise around 30,000 years ago. The wide variation of the MC1R gene exists in people of European descent because of the lack of strong environmental pressures on the gene.[8] The original allele of MC1R is coded for dark skin with a high melanin content in the cells. The high melanin content is protective in areas of high UV light exposure.[8] The need was less as humans moved into higher latitudes where incoming sunlight has lower UV light content. The adaptation of lighter skin is needed so that individuals in higher latitudes can still absorb enough UV for the production of vitamin D.[8] Freckled individuals tend to tan less and have very light skin, an adaptation to allow individuals that expressed these genes to synthesise sufficient vitamin D. Freckles on a female face after summertime. Types edit Ephelides describes a freckle that is flat and light brown or red and fades with a reduction of sun exposure. Ephelides are more common in those with light complexions, although they are found on people with a variety of skin tones. The regular use of sunblock can inhibit their development. Liver spots (also known as sunspots and lentigines) look like large freckles, but they form after years of exposure to the sun. Liver spots are more common in older people. See also edit Beauty mark List of Mendelian traits in humans Melanocortin 1 receptor Mole References edit ^ Kumar, Vinay, ed. (2005). Robbins and Cotran Pathologic Basis of Disease (7th ed.). Philadelphia: Elsevier Saunders. p. 1232. ISBN 0-8089-2302-1. ^ Hanson, K. M; Gratton, E; Bardeen, C. J (2006). "Sunscreen enhancement of UV-induced reactive oxygen species in the skin" (PDF). Free Radical Biology and Medicine. 41 (8): 1205–12. doi:10.1016/j.freeradbiomed.2006.06.011. PMID 17015167. ^ Garland C, Garland F, Gorham E (1992). "Could sunscreens increase melanoma risk?". Am J Public Health. 82 (4): 614–5. doi:10.2105/AJPH.82.4.614. PMC 1694089. PMID 1546792. ^ a b Flanagan N.; et al. (2000). "Pleiotropic effects of the melanocortin 1 receptor (MC1R) gene on human pigmentation". Human Molecular Genetics. 9 (17): 2531–2537. doi:10.1093/hmg/9.17.2531. PMID 11030758. ^ a b Bastiaens M.; et al. (2001). "The melanocortin-1-receptor gene is the major freckle gene". Human Molecular Genetics. 10 (16): 1701–1708. doi:10.1093/hmg/10.16.1701. PMID 11487574. ^ Box, N. F; Duffy, D. L; Irving, R. E; Russell, A; Chen, W; Griffyths, L. R; Parsons, P. G; Green, A. C; Sturm, R. A (2001). "Melanocortin-1 Receptor Genotype is a Risk Factor for Basal and Squamous Cell Carcinoma". Journal of Investigative Dermatology. 116 (2): 224–229. doi:10.1046/j.1523-1747.2001.01224.x. PMID 11179997. ^ Yamaguchi, Kyoko; Watanabe, Chiaki; Kawaguchi, Akira; Sato, Takehiro; Naka, Izumi; Shindo, Misaki; Moromizato, Keiichi; Aoki, Kenichi; Ishida, Hajime; Kimura, Ryosuke (2012). "Association of melanocortin 1 receptor gene (MC1R) polymorphisms with skin reflectance and freckles in Japanese". Journal of Human Genetics. 57 (11): 700–708. doi:10.1038/jhg.2012.96. PMID 22854540. ^ a b c Harding, R. M.; et al. (2000). "Evidence for variable selective pressures at MC1R". American Journal of Human Genetics. 66 (4): 1351–1361. doi:10.1086/302863. PMC 1288200. PMID 10733465. External links edit Classification D ICD-10: L81.2ICD-9-CM: 709.09OMIM: 266300MeSH: D008548External resources eMedicine: article/1119293 Wikimedia Commons has media related to Freckles. MedicineNet.com: Freckles Ephelides (Freckles) at eMedicine vte Growths Epidermal Wart Callus Seborrheic keratosis Acrochordon Molluscum contagiosum Actinic keratosis Squamous-cell carcinoma Basal-cell carcinoma Merkel-cell carcinoma Nevus sebaceous Trichoepithelioma Pigmented Freckles Lentigo Melasma Nevus Melanoma Dermal andsubcutaneous Epidermal inclusion cyst Hemangioma Dermatofibroma (benign fibrous histiocytoma) Keloid Lipoma Neurofibroma Xanthoma Kaposi's sarcoma Infantile digital fibromatosis Granular cell tumor Leiomyoma Lymphangioma circumscriptum Myxoid cyst Rashes With epidermal involvement Eczematous Contact dermatitis Atopic dermatitis Seborrheic dermatitis Stasis dermatitis Lichen simplex chronicus Darier's disease Glucagonoma syndrome Langerhans cell histiocytosis Lichen sclerosus Pemphigus foliaceus Wiskott–Aldrich syndrome Zinc deficiency Scaling Psoriasis Tinea (Corporis Cruris Pedis Manuum Faciei) Pityriasis rosea Secondary syphilis Mycosis fungoides Systemic lupus erythematosus Pityriasis rubra pilaris Parapsoriasis Ichthyosis Blistering Herpes simplex Herpes zoster Varicella Bullous impetigo Acute contact dermatitis Pemphigus vulgaris Bullous pemphigoid Dermatitis herpetiformis Porphyria cutanea tarda Epidermolysis bullosa simplex Papular Scabies Insect bite reactions Lichen planus Miliaria Keratosis pilaris Lichen spinulosus Transient acantholytic dermatosis Lichen nitidus Pityriasis lichenoides et varioliformis acuta Pustular Acne vulgaris Rosacea Folliculitis Impetigo Candidiasis Gonococcemia Dermatophyte Coccidioidomycosis Subcorneal pustular dermatosis Hypopigmented Tinea versicolor Vitiligo Pityriasis alba Postinflammatory hyperpigmentation Tuberous sclerosis Idiopathic guttate hypomelanosis Leprosy Hypopigmented mycosis fungoides Without epidermal involvement Red Blanchable Erythema Generalized Drug eruptions Viral exanthems Toxic erythema Systemic lupus erythematosus Localized Cellulitis Abscess Boil Erythema nodosum Carcinoid syndrome Fixed drug eruption Specialized Urticaria Erythema (Multiforme Migrans Gyratum repens Annulare centrifugum Ab igne) Nonblanchable Purpura Macular Thrombocytopenic purpura Actinic/solar purpura Papular Disseminated intravascular coagulation Vasculitis Indurated Scleroderma/morphea Granuloma annulare Lichen sclerosis et atrophicus Necrobiosis lipoidica Miscellaneous disorders Ulcers Hair Telogen effluvium Androgenic alopecia Alopecia areata Systemic lupus erythematosus Tinea capitis Loose anagen syndrome Lichen planopilaris Folliculitis decalvans Acne keloidalis nuchae Nail Onychomycosis Psoriasis Paronychia Ingrown nail Mucous membrane Aphthous stomatitis Oral candidiasis Lichen planus Leukoplakia Pemphigus vulgaris Mucous membrane pemphigoid Cicatricial pemphigoid Herpesvirus Coxsackievirus Syphilis Systemic histoplasmosis Squamous-cell carcinoma vte Hypo-/leucism Loss ofmelanocytes Vitiligo Quadrichrome vitiligo Vitiligo ponctué Syndromic Alezzandrini syndrome Vogt–Koyanagi–Harada syndrome Melanocytedevelopment Piebaldism Waardenburg syndrome Tietz syndrome Loss of melanin/amelanism Albinism Oculocutaneous albinism Ocular albinism Melanosometransfer Hermansky–Pudlak syndrome Chédiak–Higashi syndrome Griscelli syndrome Elejalde syndrome Griscelli syndrome type 2 Griscelli syndrome type 3 Other Cross syndrome ABCD syndrome Albinism–deafness syndrome Idiopathic guttate hypomelanosis Phylloid hypomelanosis Progressive macular hypomelanosis Leukoderma w/ohypomelanosis Vasospastic macule Woronoff's ring Nevus anemicus Ungrouped Nevus depigmentosus Postinflammatory hypopigmentation Pityriasis alba Vagabond's leukomelanoderma Yemenite deaf-blind hypopigmentation syndrome Wende–Bauckus syndrome Hyper- Melanin/Melanosis/Melanism Reticulated Dermatopathia pigmentosa reticularis Pigmentatio reticularis faciei et colli Reticulate acropigmentation of Kitamura Reticular pigmented anomaly of the flexures Naegeli–Franceschetti–Jadassohn syndrome Dyskeratosis congenita X-linked reticulate pigmentary disorder Galli–Galli disease Revesz syndrome Diffuse/circumscribed Lentigo/Lentiginosis: Lentigo simplex Liver spot Centrofacial lentiginosis Generalized lentiginosis Inherited patterned lentiginosis in black persons Ink spot lentigo Lentigo maligna Mucosal lentigines Partial unilateral lentiginosis PUVA lentigines Melasma Erythema dyschromicum perstans Lichen planus pigmentosus Café au lait spot Poikiloderma (Poikiloderma of Civatte Poikiloderma vasculare atrophicans) Riehl melanosis Linear Incontinentia pigmenti Scratch dermatitis Shiitake mushroom dermatitis Other/ungrouped Acanthosis nigricans Freckle Familial progressive hyperpigmentation Pallister–Killian syndrome Periorbital hyperpigmentation Photoleukomelanodermatitis of Kobori Postinflammatory hyperpigmentation Transient neonatal pustular melanosis Otherpigments Iron Hemochromatosis Iron metallic discoloration Pigmented purpuric dermatosis Schamberg disease Majocchi's disease Gougerot–Blum syndrome Doucas and Kapetanakis pigmented purpura/Eczematid-like purpura of Doucas and Kapetanakis Lichen aureus Angioma serpiginosum Hemosiderin hyperpigmentation Othermetals Argyria Chrysiasis Arsenic poisoning Lead poisoning Titanium metallic discoloration Other Carotenosis Tar melanosis Dyschromia Dyschromatosis symmetrica hereditaria Dyschromatosis universalis hereditaria See also Skin color Skin whitening Tanning Sunless Tattoo removal Depigmentation Retrieved from "https://en.wikipedia.org/w/index.php?title=Freckle&oldid=1114487026" Categories: Skin pigmentationSkin conditions resulting from physical factorsMelanocytic nevi and neoplasms Hidden categories: Articles with short descriptionShort description matches WikidataArticles needing additional references from February 2022All articles needing additional referencesShort description is different from WikidataCommons category link is on Wikidata Navigation menu br