Melasma
Biology of melanocyteDendritic 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 : pheomelaninMelanin synthesis
Binding Melanocyte Melanocortin 1 stimulating hormone receptor adenylase cyclase Tyrosinase cAMPMelanin synthesis
Tyrosine tyrosinase Dopa Dopa quinone Eumelanin PheomelaninMelanin synthesis
MSH MC1R mutation of MC1REumelanin Pheomelanin
Melanin transfer
Phagocytosis : melanin transfer to dermis : phagocytose by melanophage Endocytosis : melanin transfer to keratinocyte via intercellular spaceMelasma
Acquired bilateral symmetrical hypermelonosis Irregular light to gray brown macule and patch Ill defined margin Involved sun exposure area Most common in womenMelasma 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%) :chinCause 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 processDermal melasma
Blue gray color Perivascular melanophage at superficial and middermis Melanin granule in dermisWhether 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.