Melasma Overview and Causes

Melasma Overview

• 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)

Causes of Melasma

• 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

Medications and External Factors

• 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

Clinical Features of Melasma

• 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).

Types of Melasma

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

Epidermal Melasma

• 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

Dermal Melasma

• Ill-defined borders
• Light brown to blue-grey colour
• Wood lamp: No accentuation
• Dermoscopy: Reticuloglobular

Mixed Melasma

• Combination of blue-grey, light and dark brown colours
• Mixed patterns with wood lamp and dermatoscope
• Treatment often shows partial improvement

Melasma Diagnosis

• 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

Melasma Differential Diagnosis

• May mimic other skin conditions such as:
  • Post-inflammatory hyperpigmentation
  • Solar lentigo
  • Other lentigines
  • Acquired dermal macular hyperpigmentation
  • Drug-induced hyperpigmentation
  • Naevus of Ota and naevus of Hori.

Melasma Treatment

• 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

Topical Therapy

• 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

Oral Treatment

• 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

Procedural Techniques

• 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).

Monitoring Treatment Response

• Serial photography and severity indices (e.g., MASI or modified MASI) can be used to monitor treatment response.