Melasma

Synonyms: chloasma, mask of pregnancy, chloasma medicamentosum

Previously known as chloasma (which originally comes from the Greek chloazein, to be green), melasma is now considered to be the better term (melas is Greek for black).

What is melasma?

Melasma is a common acquired condition of hyperpigmentation, typically occurring on the face. Multiple aetiologies, including light exposure, hormonal influences, and family history, have been implicated in pathogenesis.¹ It is thought that UV radiation, in combination with hormonal factors, acts on people with a genetic predisposition to result in abnormal melanocyte activation leading to excess melanogenesis.²

Who gets melasma? (Epidemiology)¹³

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

• Women are much more likely to be affected by men, with men making up about 10% of the diagnoses.²

• It is rare prior to puberty and tends to develop between the ages of 20 and 50.

• It is more common in Fitzpatrick skin types III to V.⁴

Risk factors for melasma⁵

These include:

• Fitzpatrick skin types 3, 4 and 5 - 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%.⁶ 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 has long been linked to oral contraceptive use⁷but more recent data also shows a link with contraceptive implants.⁸ Both progesterone only and combined oral contraceptives appear to be implicated.⁹All studies suggest that the hormonal intra-uterine systems are less likely to cause melasma, although they can do so.

  • 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 and may 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. Commonly used medications which can result in melasma include metronidazole, clarithromycin, finasteride, anastrazole and paroxetine. ⁷¹⁰

Melasma symptoms¹

• Patients usually complain of a gradual onset of areas of darker skin.

• Gradual onset is typical with episodic worsening during periods of increased UV or visible-light exposure.

• Typically melasma consists of symmetrical, hyperpigmented macules and patches with irregular borders and uniform coloration, predominantly affecting the face.

• Classic facial distribution patterns include centrofacial, malar, and mandibular involvement

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

Images of melasma are available on the DermNet and Primary Care Dermatology Society websites.³¹¹

Differential diagnosis³

• 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. Dermoscopy may be useful.

Melasma treatment and management³¹¹

General

• Sunlight is a considerable aggravating factor - year-round sun protection should be advised, including high factor sun creams. Sun creams containing iron oxide have been shown to be beneficial.¹

• Mild cases may simply require reassurance.

• Camouflage with cosmetics may be helpful.

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

• Consider changing contraceptive type, although pregnancy is also a significant risk in susceptible women.

• Review the medication in case of a drug-related cause.

Topical melasma treatments

• Most treatments are unavailable on the NHS for treating melasma. No medications are licensed in the UK for melasma.

• Hydroquinone 2-4% is a skin-lightening agent which inhibits conversion of dopa to melanin. It is applied to the affected areas at night for 2-4 months. It is not licensed in the UK but is available to be prescribed by NHS dermatologists on some local formularies (but by no means all).

• 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 treated.¹² It may cause erythema and scaling. This is also available in some areas for NHS dermatologists to prescribe

• Cysteamine is a known potent depigmenting agent which has shown significant efficacy (as 5% cream) in the treatment of patients with epidermal melasma.¹³

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

• Ascorbic acid (vitamin C).

• Tranexamic acid can be used either orally or topically, off-label and privately.¹³¹⁴

• Tyrosinase inhibitors.

• A variety of newer treatments are thought to have the potential to treat melasma but have not yet been studied adequately. These include thiamidol, kojic acid and arbutin.¹⁵

Chemical peels

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

Laser treatment¹⁶

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

• Fractional lasers

• Q-switched Nd:YAG lasers

• Intense pulsed light

Prognosis¹

Melasma typically follows a chronic, relapsing course. Significant improvement is often achieved with consistent therapy, but complete and durable clearance is less predictable without long-term maintenance

Melasma associated with pregnancy usually resolves spontaneously within a year.

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.