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 hormon receptor

adenylase cyclase


Tyrosinase cAMP
Binding
Melanocyte Melanocortin 1 stimulating hormon receptor

adenylase cyclase

Tyrosinase cAMP

Melanin synthesis
Tyrosine
tyrosinase
Dopa

Dopa quinone

Eumelanin Pheomelanin
Tyrosine
tyrosinase
Dopa

Dopa quinone

Eumelanin Pheomelanin

Melanin synthesis

MSH

MC1R mutation of MC1R

Eumelanin Pheomelanin
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.
HQ 5%, tretinoin 0.1%, and dexamethasone 0.1%, was first introduced in 1975 and termed the Kligman formula
combination of HQ 4%, tretinoin 0.05%, and fluocinolone acetonide 0.01% (Tri-Luma®, Galderma) proved better than any combination of two of the above agents, with 77% of patients showing complete or nearly complete clearing.
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