Chloasma

Synonyms: Melasma, Mask of pregnancy, Chloasma Medicamentosum

Chloasma comes from the Greek chloazein, to be green. It is considered to be something of a misnomer, and many dermatologist prefer the term melasma (melas is Greek for black). The pathophysiology is largely unknown but many differences have been noted between melasma and normal skin. There is, for example, an increase in the level of melanin, large numbers of melanocytes and melanosomes, and increased synthesis of tyrosinase.¹

The exact incidence of chloasma is unknown, but it is a common condition.There is a female to male predilection, with a ratio of 9:1.²

Risk Factors

These include:
Dark skin - it is common in Asians and Hispanics.²
Hormonal - chloasma occurs commonly in pregnancy. One study in Iran found a prevalence among 400 pregnant patients of 15.8%.³ It is rare before puberty and is commonest in women during their reproductive years.² It is linked to use of oral contraceptives.⁴ One study of patients with chloasma found that the frequency of thyroid disorders was four times greater compared to a control group.⁵
Sun exposure - this is a well established risk factor.⁴ Chloasma occurs in sun-exposed areas of the skin.²
Genetics - 30% of patients report a positive family history, and identical twins with chloasma have been reported.²
AIDS - one study reported a group of AIDS patients who developed chloasma-like hyperpigmentation of the face.

Patients usually complain of gradual onset areas of dark skin. The colour may vary from tan to brown, but may be black or have a bluish tinge. The distribution is usually symmetrical. Three patterns are commonly seen - centrofacial, malar or mandibular.

• Addison Disease
• Drug-Induced Photosensitivity
• Lupus Erythematosus, Discoid
• Mastocytosis (mast cell proliferation and accumulation within various organs, most commonly the skin)
• Poikiloderma of Civatte (erythema associated with a mottled pigmentation seen on the sides of the neck, more commonly in women)

Wood's light helps to locate the pigmentation in the dermis or epidermis. In many cases, it is found in both locations.²

Chloasma is a difficult condition to manage, as sunlight is a considerable aggravating factor and it is difficult to prevent exposure even with high factor protection creams.
A variety of treatment approaches have been tried. The best seems to be the use of lightening agents. Hydroxyquinone 4% is the commonest used.⁶ Sometimes a peeling agent such as glycolic acid is added.⁷ Other lightening agents that have been tried include tretinoic acid, ascorbic acid, and azelaic acid either alone or in combination. None seem to be superior to 4% hydroxyquinone.²Laser treatment and intense pulse light therapy is also sometimes employed to hasten resolution.⁶

Most cases resolve eventually, but can take a long time to do so. Continued exposure to sunlight tends to hamper treatment and lead to recurrence. Resolution will also take longer in patients with extensive dermal melanin compared to those in whom pigmentation is mainly in the epidermal layer.²