Melasma

Synonyms: chloasma, mask of pregnancy, chloasma medicamentosum

The word chloasma comes from the Greek chloazein, to be green. It is considered to be something of a misnomer and so increasingly dermatologists prefer the term melasma (melas is Greek for black).

What is melasma?

Melasma is a common acquired condition of symmetrical hyperpigmentation, typically occurring on the face. Multiple aetiologies, including light exposure, hormonal influences, and family history, have been implicated in pathogenesis¹ .

Who gets melasma? (Epidemiology)^{2 3}

• The exact incidence of melasma is unknown but it is a common condition. Prevalence varies significantly geographically.

• There is a female:male predilection in a ratio of 9:1, although this varies depending on the population studied.

• It is more common in darker skin types and less common in fair or very dark skin.

• It may occur in any population but is more common in those of East Asian, Indian, Pakistani, Middle Eastern and Mediterranean-African, Hispanic-American and Brazilian origin.

Risk factors for melasma

These include:

• Dark skin types. (Fitzpatrick skin types 3 and 4 - that is, the type of skin which is naturally brown or tans very well.)

• Hormonal factors:

  • Melasma occurs commonly in pregnancy. One study in Iran found a prevalence, among 400 pregnant women, of 15.8%⁴ . In Pakistan, it has been shown to be as high as 46% and in other studies up to 70%.

  • Melasma associated with pregnancy usually resolves spontaneously within a year of delivery.

  • It is rare before puberty and is most common in women during their reproductive years. It is linked to use of oral contraceptives, although some studies suggest this may not be as significant as previously thought⁵ .

  • There is also an association with thyroid autoimmunity.

• Sun exposure. This is a well-established risk factor. Melasma occurs in sun-exposed areas of the skin. It tends to improve in winter and worsen after sun exposure.

• Genetics. Up to 40% of patients report a positive family history and identical twins with chloasma have been reported.

• Medication. Pigmentation changes similar to melasma are seen with phenytoin use.

• Other pigmented lesions. One study found a higher incidence of melasma in women who also had lentigines or melanocytic naevi⁶ .

Melasma symptoms³

• Patients usually complain of gradual-onset areas of dark skin.

• The pigmentation mainly occurs on the face and is usually bilateral.

• The colour may vary from tan to brown but may be black or have a bluish tinge.

• The distribution is usually symmetrical and three patterns are commonly seen - centrofacial, malar or mandibular.

Images of melasma are available on the DermNet New Zealand and Primary Care Dermatology Society websites^{2 7} .

Differential diagnosis^{2 3}

• Addison's disease.

• Haemochromatosis.

• Drug-induced photosensitivity. Drug reactions can cause hyperpigmentation via a number of processes.

• Maturational dyschromia. (Age-related diffuse discolouration caused by cumulative ultraviolet exposure.)

• Discoid lupus erythematosus.

• 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).

• Lichen planus pigmentosus.

• Freckles.

• Solar lentigo

• Naevus of Oti (blue/grey to slate-brown patches of hyperpigmentation, usually unilateral and usually presenting in infancy or puberty).

• Naevus of Hori (bilateral symmetrical blue-grey or grey-brown macules on the cheeks, presenting in adults).

Investigations

Diagnosis is essentially clinical. Wood's light helps to locate the pigmentation in the dermis or epidermis. In many cases it is found in both locations. Occasionally skin biopsy is performed.

Melasma treatment and management^{2 7 8}

General

• Melasma is a difficult skin condition to manage, as sunlight is a considerable aggravating factor and it is difficult to prevent exposure even with high-factor protection creams.

• However, year-round sun protection should be advised. (Hats and high factor sun cream, especially for the face.)

• Mild cases may simply require reassurance.

• Camouflage with cosmetics may be helpful.

• Melasma associated with pregnancy should resolve spontaneously within a few months.

• If there is any evidence of the condition being related to hormonal contraception, consider changing this.

• Review medication in case any cause can be found.

• Various possible therapies are available but usually specialist referral should be considered. Many treatments are only provided on a private basis.

Topical melasma treatments

• Skin-lightening agents, particularly hydroquinone 2-4%. It inhibits conversion of dopa to melanin. It is applied to the affected areas at night for 2-4 months. It is more effective in combination with other agents. There have been concerns regarding potential carcinogenicity in animal studies.

• Triple therapy cream containing hydroquinone, tretinoin and fluocinolone acetonide has been found in one study to be more cost-effective than hydroquinone alone and benefits 60-80% of those treated⁹ . In the UK it is prescribed as Pigmanorm® but usually is prescribed privately and is not licensed in the UK. It may cause erythema and scaling.

• Cysteamine is a known potent depigmenting agent which has shown significant efficacy (as 5% cream) in the treatment of patients with epidermal melasma¹⁰ .

• Azelaic acid. This is applied twice daily and may be used long-term. It may sting.

• Ascorbic acid (vitamin C). This works through copper by inhibiting pigment production. Copper is needed in the melanin synthesis pathway. Kojic acid is also sometimes added to preparations as it binds copper.

• Tranexamic acid can be used either orally or topically.

• Tyrosinase inhibitors. A number of agents affect tyrosinase and other factors of the melanin synthesis pathway. Agents which have been used include 4-n-butylresorcinol and oligopeptides.

Chemical peels

• Chemical peels containing glycolic acid or trichloroacetic acid are used by dermatologists. They may cause a skin reaction.

• Tretinoin alone is used as a peel.

Laser treatment

A number of types of laser therapy have been used including:

• Fractional lasers

• Q-switched Nd:YAG lasers

• Intense pulsed light

Prognosis

Melasma associated with pregnancy usually resolves spontaneously within a year. Many cases resolve eventually but can take a long time to do so. Few treatments are completely successful. Continued exposure to sunlight tends to hamper treatment and lead to recurrence.

Melasma may negatively affect quality of life because of the effect on appearance, particularly because it tends to be on the face, with consequent psychosocial sequelae. It is not, however, a premalignant condition and it is primarily a cosmetic issue.