Melasma (chloasma or the mask of pregnancy when present in pregnant women) is a tan or dark facial skin discoloration. Although it can affect anyone, melasma is particularly common in women, especially pregnant women and those who are taking oral contraceptives or hormone replacement therapy medications.

Symptoms

The symptoms of melasma are dark, irregular patches commonly found on the upper cheek, nose, lips, and forehead. These patches often develop gradually over time. Melasma does not cause any other symptoms beyond the cosmetic discoloration.

Cause

Melasma is thought to be the stimulation of melanocytes or pigment-producing cells by the female sex hormones estrogen and progesterone to produce more melanin pigments when the skin is exposed to sun. Women with a light brown skin type who are living in regions with intense sun exposure are particularly susceptible to developing this condition.

Genetic predisposition is also a major factor in determining whether someone will develop melasma.

The incidence of melasma also increases in patients with thyroid disease . It is thought that the overproduction of melanocyte-stimulating hormone (MSH) brought on by stress can cause outbreaks of this condition. Other rare causes of melasma include allergic reaction to medications and cosmetics.

Diagnosis

Melasma is usually diagnosed visually or with assistance of a Wood lamp (340 - 400 nm wavelength). Under Wood lamp, excess melanin in the epidermis can be distinguished from that of the dermis.

Treatment

The discoloration usually go away spontaneously over a period of several months after giving birth or stopping the oral contraceptives or hormone replacement therapy.

Treatments to hasten the fading of the discolored patches include:

• Topical depigmenting agents, such as hydroquinone (HQ) either in over-the-counter (2%) or prescription (4%) strength. HQ is a chemical that inhibits tyrosinase, an enzyme involved in the production of melanin.

• Tritenoin , an acid that increases skin cell (keratinocyte) turnover. This treatment cannot be used during pregnancy.

• Azelaic acid (20%), thought to decrease the activity of melanocytes.

• Facial peel with alpha hydroxyacids or chemical peels with glycolic acid .

• Laser treatment

In all of these treatments the effects are gradual and a strict avoidance of sunlight is required. The use of broad-spectrum sunscreens with physical blockers, such as titanium dioxide and zinc dioxide is preferred over that with only chemical blockers. This is because UV-A, UV-B and visible lights are all capable of stimulating pigment production.

Cosmetic cover-ups can also be used to reduce the appearance of melasma.

See also

• Linea nigra

External links

• MedlinePlus - Melasma
• DermNet NZ - Chloasma
• Health In Plain English - Melasma or Chloasma
• eMedicine - Melasma