dermatologic disorders
Hyperpigmentation
Melasma (Chloasma)
Melasma consists of dark brown, roughly symmetric patches of hyperpigmentation with irregular borders on the face (usually on the forehead, temples, cheeks, cutaneous upper lip, or nose). It occurs primarily in pregnant women (melasma gravidarum, also called the mask of pregnancy) and in women taking Oral Contraceptives . Ten percent of cases occur in nonpregnant women and dark-skinned men. Melasma is more prevalent among and lasts longer in people with dark skin. Because melasma risk increases with increasing sun exposure, the mechanism probably involves overproduction of melanin by hyperfunctional melanocytes. Other than sun exposure, aggravating factors include Autoimmune thyroid disorders Photosensitizing drugs In women, melasma fades slowly and incompletely after childbirth or cessation of hormone use. In men, melasma rarely fades. can enhance protection ( Melasma references , Other treatment depends on whether the pigmentation is epidermal or dermal; epidermal pigmentation becomes accentuated with a Wood Light (365 nm) or can be diagnosed with biopsy. Only epidermal pigmentation responds to treatment. Most topical melasma treatments are used in combination rather than individually. Triple topical therapyis first-line treatment that is often effective and consists of a combination of Hydroquinone2 to 4% Tretinoin0.05 to 1% A class V to VII topical corticosteroid ( see Table: Relative Potency of Selected Topical Corticosteroids ) Hydroquinonedepigments the skin by blocking the enzymatic oxidation of tyrosine 3,4-dihydroxyphenylalanine (DOPA) and inhibiting melanocyte metabolic processes.Hydroquinoneshould be tested behind one ear or on a small patch on the forearm for 1 week before use on the face because it may cause irritation or an allergic reaction.Tretinoinpromotes keratinocyte turnover and can exfoliate skin that contains epidermal pigment. Corticosteroids help block synthesis and secretion of melanin. Two promising technologies being tried in conjunction with triple topical therapy are the Q-switched Nd:YAG (1064 nm) laser and nonablative fractional resurfacing. If triple topical therapy is not available, thenhydroquinone3 to 4% applied twice a day for up to 8 weeks at a time (chronic continuous use can theoretically increase the risk of exogenous ochronosis, which is a permanent form of hyperpigmentation) may be considered; 2%hydroquinoneis useful as maintenance. Azelaic acid15 to 20% cream can be used in place of or withhydroquinoneand/ortretinoin.Azelaic acidis a tyrosinase inhibitor that reduces melanin production. In addition, topical kojic acid has been increasingly used; it is a chelating agent that blocks tyrosine conversion to melanin. During pregnancy,azelaic acid15 to 20% cream and chemical peeling with glycolic acid are safe to use.Hydroquinoneandtretinoinare not safe to use. Second-line treatment options for patients with severe melasma unresponsive to topical bleaching agents include chemical peeling with glycolic acid or 30 to 50%trichloroacetic acid. Laser treatments also have been used but are not standard therapy. in patients with moderate-to-severe melasma ( Melasma references ). 1.Goh CL, Chuah SY, Tien S, et al: Double-blind, placebo-controlled trial to evaluate the effectiveness ofPolypodium leucotomosextract in the treatment of melasma in Asian skin: A pilot study.J Clin Aesthet Dermatol11(3):14-19, 2018. Epub 2018 Mar 1. PMID: 29606995; PMCID: PMC5868779 2.Lim HW, Kohli I, Ruvolo E, et al: Impact of visible light on skin health: The role of antioxidants and free radical quenchers in skin protection.J Am Acad Dermatol86(3S):S27-S37, 2022. doi: 10.1016/j.jaad.2021.12.024 3.DiNardo JC, Downs CA: Dermatological and environmental toxicological impact of the sunscreen ingredient oxybenzone/benzophenone-3.J Cosmet Dermatol17(1):15-19. doi: 10.1111/jocd.12449 4.Del Rosario E, Florez-Pollack S, Zapata L Jr, et al: Randomized, placebo-controlled, double-blind study of oraltranexamic acidin the treatment of moderate-to-severe melasma.J Am Acad Dermatol78(2):363–369, 2018. doi: 10.1016/j.jaad.2017.09.053 