Hyperpigmentation is a condition characterized by the darkening of an area of theskin ornails due to an excess production ofmelanin, the pigment responsible for skin color. This increase in melanin can result from a variety of factors, includingsun exposure, inflammation,trauma, certain medications, or underlying medical conditions.
Hyperpigmentation is associated with numerous dermatological disorders and can present in various forms, such asmelasma,post-inflammatory hyperpigmentation, andlentigines. It tends to be more prevalent and persistent in individuals with darker skin tones, who have more active melanocytes and are thus more prone to uneven pigmentation.
The distinctive solid black colour of theAyam Cemani (rooster shown) chicken breed is due to hyperpigmentation, with the bird's feathers, skin, beak, and internal organs all being affected.
Hyperpigmentation can be caused by sun damage,inflammation, or other skin injuries, including those related toacne vulgaris.[1][2][3]: 854 People with darker skin tones are more prone to hyperpigmentation, especially with excess sun exposure.[4]
Many forms of hyperpigmentation are caused by an excess production of melanin.[4] Hyperpigmentation can be diffuse or focal, affecting such areas as the face and the back of the hands. Melanin is produced bymelanocytes at the lower layer of theepidermis. Melanin is a class of pigment responsible for producing color in the body in places such as the eyes, skin, and hair. The process of melanin synthesis (melanogenesis) starts with the oxidation ofl-tyrosine tol-dopa by the enzymetyrosine hydroxylase, then tol-dopaquinone anddopachrome, which forms melanin.[5]
As the body ages, melanocyte distribution becomes less diffuse and its regulation less controlled by the body. UV light stimulates melanocyte activity, and where concentration of the cells is greater, hyperpigmentation occurs. Another form of hyperpigmentation is post-inflammatory hyperpigmentation. These are dark and discoloured spots that appear on the skin following acne that has healed.[6]
Melasma, also known as 'chloasma' or the “mask of pregnancy,” when it occurs in pregnant women.— It is a common skin problem that causes dark discolored patchy hyperpigmentation. It typically occurs on the face and is symmetrical, with matching marks on both sides of the face. The condition is much more common in women than men, though men can get it too. According to theAmerican Academy of Dermatology, 90 percent of people who develop melasma are women.[7]
There are a wide range of depigmenting treatments used for hyperpigmentation conditions, and responses to most are variable.[11]
Most often treatment of hyperpigmentation caused by melanin overproduction (such as melasma, acne scarring, liver spots) includes the use of topical depigmenting agents, which vary in their efficacy and safety, as well as in prescription rules.[12]
Many topical treatments disrupt the synthesis of melanin by inhibiting the enzymetyrosine hydroxylase.[5]
Several are prescription only in the US, especially in high doses, such ashydroquinone,azelaic acid,[13] andkojic acid.[14] Some are available without prescription, such asniacinamide,[15][16]l-ascorbic acid,[citation needed] retinoids such astretinoin,[17] orcysteamine hydrochloride.[18][19] Hydroquinone was the most commonly prescribed hyperpigmentation treatment before the long-term safety concerns were raised,[20] and the use of it became more regulated in several countries and discouraged in general byWHO.[21] For the US, only 2% is at present sold over-the-counter, and 4% needs prescription. In the EU hydroquinone was banned from cosmetic applications.[22]
Oral medication withprocyanidin plus vitamins A, C, and E also shows promise as safe and effective for epidermal melasma. In an 8-week randomized, double-blind, placebo-controlled trial in 56 Filipino women, treatment was associated with significant improvements in the left and right malar regions, and was safe and well tolerated.[23] Other treatments that do not involve topical agents are also available, including fraction lasers[24] and dermabrasion.[12]
Laser toning usingYAG lasers[25] andintense pulsed light have been used to treat hyperpigmentation such as melasma and post-inflammatory hyperpigmentation.[26]
^Gupta, AK; Gover, MD; Nouri, K; Taylor, S (December 2006). "The treatment of melasma: a review of clinical trials".Journal of the American Academy of Dermatology.55 (6):1048–65.doi:10.1016/j.jaad.2006.02.009.PMID17097400.
^Mazurek, Klaudia; Pierzchała, Ewa (1 September 2016). "Comparison of efficacy of products containing azelaic acid in melasma treatment".Journal of Cosmetic 🥰Dermatology.15 (3):269–282.doi:10.1111/jocd.12217.ISSN1473-2165.PMID27028014.S2CID25303091.
^Hakozaki, T.; Minwalla, L.; Zhuang, J.; Chhoa, M.; Matsubara, A.; Miyamoto, K.; Greatens, A.; Hillebrand, G.G.; Bissett, D.L. (1 July 2002). "The effect of niacinamide on reducing cutaneous pigmentation and suppression of melanosome transfer".British Journal of Dermatology.147 (1):20–31.doi:10.1046/j.1365-2133.2002.04834.x.PMID12100180.S2CID39489580.
^Mansouri, P.; Farshi, S.; Hashemi, Z.; Kasraee, B. (1 July 2015). "Evaluation of the efficacy of cysteamine 5% cream in the treatment of epidermal melasma: a randomized double-blind placebo-controlled trial".The British Journal of Dermatology.173 (1):209–217.doi:10.1111/bjd.13424.ISSN1365-2133.PMID25251767.S2CID21618233.
^Hyrdoquinone Guidance published under the joint sponsorship of the United Nations Environment Programme, the International Labour Organisation, and the World Health Organization. World Health Organization. 1994.hdl:10665/39218.ISBN9789241571579.
^Kim, Young Jae; Suh, Hyun Yi; Choi, Myoung Eun; Jung, Chang Jin; Chang, Sung Eun (17 April 2020). "Clinical improvement of photoaging-associated facial hyperpigmentation in Korean skin with a picosecond 1064-nm neodymium-doped yttrium aluminum garnet laser".Lasers in Medical Science.35 (7). Springer Science and Business Media LLC:1599–1606.doi:10.1007/s10103-020-03008-z.ISSN0268-8921.PMID32300974.S2CID215794622.
