Melasma Overview and Causes

Study Notes

Melasma is a common acquired skin disorder
Characterized by bilateral, blotchy, brownish facial pigmentation
Previously called chloasma but now preferred term reflects Greek meaning of "to become green"
Often affects women more than men, typically between 20 and 40 years old
More common in people who tan easily or have naturally brown skin (Fitzpatrick skin types III, IV)

Complex disorder possibly related to photoaging in genetically predisposed individuals
Results from overproduction of melanin by melanocytes
Melanin can be taken up by keratinocytes or deposited in dermis
Factors associated with melasma:
- Family history (60% report affected family members)
- Sun exposure (UV and visible light promote melanin production)
- Hormones (Pregnancy, estrogen/progesterone-containing oral contraceptives, IUDs, implants, and hormone replacement therapy implicated in a quarter of affected women)
- Thyroid disorders

Some medications and scented products can trigger phototoxic reactions, leading to melasma
Researchers studying the role of stem cells, neural, vascular and local hormonal factors in melanocyte activation

Bilateral, asymptomatic, light-to-dark brown macules or patches
Irregular borders
Common patterns include centrofacial (forehead, cheeks, nose, upper lip, sparing the philtrum), malar (cheeks, nose), mandibular (jawline, chin), and extrafacial (forearms, upper arms, shoulders in sun-exposed areas).

Classified as epidermal, dermal, or mixed, based on level of increased melanin within the skin.

Well-defined borders
Dark brown colour
Wood lamp: More obvious
Dermoscopy: Scattered islands of brown reticular network with dark fine granules
Treatment often has good results

Usually clinical diagnosis based on appearance and examination using a Wood lamp and dermatoscope
Occasionally, skin biopsy may be required for histology
Histology typically shows melanin deposition in basal and suprabasal keratinocytes, highly dendritic melanocytes, and melanin within dermal melanophages.
May also show solar elastosis, and elastic fibre fragmentation, and an increase in blood vessels

Often involves a combination of measures
General measures include:
- Year-round sun protection (broad-brimmed hat, broad-spectrum high SPF sunscreen, avoiding sun exposure)
- Discontinuing hormonal contraception if possible
- Cosmetic camouflage

Successful topical treatment usually includes a combination of hydroquinone, tretinoin, and moderate-potency topical steroids (often skin lightening creams)
Other topical agents sometimes used alone or in combination include:
- Azelaic acid
- Kojic acid
- Cysteamine cream
- Ascorbic acid
- Methimazole
- Tranexamic acid
- Glutathione
- Soybean extract

Tranexamic acid blocks the conversion of plasminogen to plasmin, which can have effects in inhibiting prostaglandin and factors involved in melasma
More new oral treatments are currently under investigation

Chemical peels and lasers may be used with caution as these can worsen melasma or cause post-inflammatory hyperpigmentation
Patients may be pretreated with tyrosinase inhibitors, such as hydroquinone
Superficial epidermal pigment can be peeled off with alpha-hydroxy acids (AHAs) or beta-hydroxy acids (BHAs).