Melasma

Melasma

Biology of melanocyte
Dendritic cell at basal layer of epidermis Produce melanin and send to surrounding keratinocyte Epidermal melanin unit (melanocyte:keratinocyte) = 1:36

Biology of melanin

Synthesis from melanosome Transport to keratinocyte via dendritic process of melanocyte 2 type : eumelanin : pheomelanin

Melanin synthesis

Binding Melanocyte Melanocortin 1 stimulating hormone receptor adenylase cyclase Tyrosinase cAMP

Melanin synthesis

Tyrosine tyrosinase Dopa Dopa quinone Eumelanin Pheomelanin

Melanin synthesis

MSH MC1R mutation of MC1R


Eumelanin Pheomelanin

Melanin transfer

Phagocytosis : melanin transfer to dermis : phagocytose by melanophage Endocytosis : melanin transfer to keratinocyte via intercellular space

Melasma

Acquired bilateral symmetrical hypermelonosis Irregular light to gray brown macule and patch Ill defined margin Involved sun exposure area Most common in women

Melasma is a common acquired pigmentary disorder that occurs mainly in women (more than 90% of cases) of all racial and ethnic groups, but particularly affects those with Fitzpatrick skin types IV–VI

Distribution of melasma

Central facial pattern (63%) : cheek, forehead, nose, chin Malar pattern (21%) : cheek, nose Mandibular pattern (16%) :chin

Cause of melasma

Light : UVA, UVB, visible light Hormone : pregnancy, contraceptive pill Drug : dilantin, anti-malarial drug, tetracycline, minocycline Cosmetic : perfume, color Genetic Malnutrition : liver dysfunction, B12 def.



Types of melasma
Epidermal melasma Dermal melasma Mixed epidermal dermal melasma


The use of a Wood’s lamp can often be very beneficial in determining the location of melanin deposition showing enhancement of color contrast in lesional skin for the epidermal type, but not the dermal types. The mixed type has enhancement in some areas of lesional skin, but not in other areas.

Estrogen may play a role in melasma induction(OCP,HRT,pregnancy) Pregnancy induced melasma will recover after some months (but not completely).

Epidermal melasma

Light or dark brown color Melanin deposition in basal, suprabasal layer of epidermis Larger melanocyte with more noticeable dendritic process

Dermal melasma

Blue gray color Perivascular melanophage at superficial and middermis Melanin granule in dermis

Whether the melanin is deposited in the epidermis or dermis is important therapeutically because dermal hyperpigmentation is much more challenging to treat

Topical Treatments for Melasma

In those patients with epidermal type melasma, there are multiple treatments available (see Table 2).6 Topical agents include phenols, e.g., hydroquinone (HQ); retinoids, e.g., tretinoin; azelaic acid; kojic acid (KA); and glycolic acid (GA).



Hydroquinon
2%–4% has been widely used for melasma therapy. inhibits the conversion of dopa to melanin by inhibitin theactivity of tyrosinase.may interfere with DNA and RNA synthesis, degrade melanosomes, and destroy melanocytes.

Reports of contact dermatitis in up to 25% As an itchy eruption it is best to be tested in a hidden part before use Side-effects included irritant and allergic contact dermatitis, PIH, nail bleaching and rarely, ochronosis-like pigmentation.

retinoids

0.05-0.1% inhibiting tyrosinase transcription,interrupting melanin synthesis. While tretinoin may be effective in reducing melasma, it typically takes at least 24 weeks to see clinical improvement.

azelaic acid

1) 15%–20% a dicarboxylic acid, is a reversible inhibitor of tyrosinase 2) shown to be as effective as HQ 4% but without its side effects.3) The combination of azelaic acid with 0.05% tretinoin or 15%–20% glycolic acid may produce earlier, more pronounced skin lightening. Adverse effects include pruritus, mild erythema, scaling, and burning.

KOJIC ACID

KA 2% is generally equivalent to other therapies but may be more irritating.

Glycolic acid

GA 5%–10% is an alpha-hydroxy acid It decreases pigment by many mechanisms including thinning the stratum corneum, enhancing epidermolysis, dispersing melanin in the basal layer of the epidermis, and increasing collagen synthesis in the dermis.

Laser treatment for melasma

Target chromophore is melanin Should destroy melanocyte in hair follicle Good in dermal and mix melasma Epidermal melanin removal : lPL Dermal melanin removal : Q-switched Ruby, Q-switched Alexandrite, Q-switched Nd:YAG