Melasma

From dermoscopedia

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 Editor: Ashfaq A. Marghoob

 Author(s): Emmanouil Chousakos
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Description This chapter describes the dermoscopic features of melasma and its subtypes.
Author(s) Emmanouil Chousakos
Responsible author Ash Marghoob→ send e-mail
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Status update June 24, 2020
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Melasma (or chloasma) is a common acquired pigmentary disorder of the skin that leads to hyperpigmentation. It is more common in women.[1] It appears as irregular, dark macules or patches, varying from brown to gray colors, arranged in a confluent or in a punctuate arrangement. It is seen mostly on the face and less commonly on other sun-exposed body sites.[2]


Melasma results from an overstimulation of intrapepidermal melanocytes resulting in increased production of melanosomes and an increase in melanosome transfer to keratinocytes. This melanocyte activation may be triggered by a numerous factors such as excessive sun exposure, pregnancy, and hormonal dysregulation.[3] Genetic susceptibility has also been observed. In addition, while less common, melasma may be associated with cosmetics, photosensitizing medication, certain foods, thyroid diseases, liver disease, ovarian tumors, parasitic infections and even stressful events.[4] Histopathology reveals melanin localized within epidermal keratinocytes and free melanin in the upper dermis and/or within melanophages.[5] Based on the melanin distribution melasma is classified as epidermal, dermal or mixed.[6][7]


Dermoscopy provides a means to assist diagnosis and classification. Dermoscopically melasma is characterized by the presence of a thin pigment network, arcuate and annular structures that spare the follicular and sweat gland openings, brown or gray globules, brown or gray granules and telangiectasias. In addition, structureless, pigmented areas may also be seen.[4][8]


Epidermal[edit]

The majority of cases of melasma are of the epidermal type. When pigment is present in the epidermis and stratum corneum then dermoscopy reveals a well-defined, dark brown pigment network with sharp delineation of margins. When pigment is concentrated in lower parts of the epidermis then dermoscopy reveals a lighter brown colored network. One can also see prominent telengiectasias in areas of epidermal melasma.[9] Under the Wood light examination enhancement is observed.[10]


Dermal[edit]

Dermoscopy reveals an ill-defined pigment network with a brownish to grey color. Additional features include annular, honeycomb or arcuate structures.[11] The dermal subtype is also associated with brown or gray granules (dots) that correspond to clusters of melanophages.[12] Under the Wood light examination no enhancement is observed.[11]


Mixed[edit]

Dermoscopy reveals a combination of features seen in both the epidermal and dermal type of melasma.


Indeterminate[edit]

Unclassified type is seen in darker skin phenotypes (>type III). Wood’s light examination in this subtype of melasma does not provide added information.[11] Dermoscopy can assist with the classification by increasing our ability to distinguish the above-mentioned features in the context of low contrast.


The dermoscopic differential diagnosis for melasma includes primarily Lichen Planus Pigmentosus, Riehl’s Melanosis and Exogenous Ochronosis.[8] LPP and Riehl’s Melanosis tend to appear on an erythematous background skin compared to melasma. Exogenous Ochronosis demonstrates darker pigmentation, often with a blue-gray granular-globular pattern with characteristic obliteration of follicular openings and curvilinear, elongated, arciform and annular structures.[9][13] Secondarily melasma should be differentiated from discoid lupus erythematosus, phototoxic dermatitis, erythema dyschromium perstans, phytophotodermatitis, pigmented contact dermatitis, drug-induced pigmentation, poikiloderma of Civatte, erythromelanosis follicularis faciei, Hori’s nevus, argyria, nevus of Ota, lentigines, ephelides, macular amyloidoses, and post-inflammatory hyperpigmentation.[14]


The features seen on dermoscopy of melasma can help outline a rational therapeutic approach. Melasma therapies range from topical therapies, chemical peels, systemic therapies, lasers, dermabrasion to microneedling.[15][16] The efficacy of the selected treatment appears to correlate with the subtype of the melasma. For example, therapies targeting the epidermis such as chemical peels or creams with depigmenting agents appear to be more effective for epidermal melasma. In contrast, dermal melasma cases appear to respond better with methods that reach the deeper layers of the skin and include treatments with lasers or microneedling. In addition, it may also help to consider the presence of specific features such as vasculature when deciding between different treatment modalities since in such cases pulse-dye lasers may prove more effective. Lastly, it goes without saying that dermoscopy can be used to monitor treatment response.[17]


Mixed subtype of melasma with predominant epidermal component and prominent telangiectasias. Image courtesy of Dr. Ahmed Sadek.


Mixed subtype of melasma with predominant epidermal component and prominent telangiectasias. Image courtesy of Dr. Ahmed Sadek.


Mixed subtype of melasma with predominant epidermal component and prominent telangiectasias. Image courtesy of Dr. Ahmed Sadek.




References

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  13. Gil I, Segura S, Martínez-Escala E, et al. Dermoscopic and Reflectance Confocal Microscopic Features of Exogenous Ochronosis. Arch Dermatol. 2010;146(9):1021–1025.
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  17. Ibrahim ZA, Gheida SF, El Maghraby GM, Farag ZE. Evaluation of the efficacy and safety of combinations of hydroquinone, glycolic acid, and hyaluronic acid in the treatment of melasma. J Cosmet Dermatol. 2015 Jun;14(2):113-23.