Atopic Dermatitis: a Short Summary
Skin color is determined by:
- The type of melanin
- The amount of melanin in melanocytes
- The distribution pattern in surrounding keratinocytes
The term melasma comes from Greek melas: black
Etiology: The exact cause is unknown but some factors play a role
- Ultraviolet light (UV)
- genetic factors
- thyroid disturbances
- cosmetics
- hormonal factors (in females)
Epidemiology
- The incidence is unknown
- It affects around 6 million people in the USA
The Prevalence is highest in
- hispanics
- East Asians
- Individuals with Phototypes Fitzpatrick IV to VI
- Individuals living in areas of intense Ultraviolet (UV) irradiation
Females are more affected than males:
- female-male ratio 9 to 1
- also men: 10% Caucasian, 26% Indians….
Types
- based on the depth of the pigment in the skin
- epidermal
- dermal
- mixed
- indeterminate
- based on distribution
- centrofacial
- malar
- mandibular
Concerning the treatment of Melasma (Chloasma) (Pregnancy Mask): what one needs to know is that sun exposure, whether only once or repeated worsens melasma (chloasma)(pregnancy mask):
- A single exposure to Ultraviolet light (UV) increases the size of melanocytes and tyrosinase activity.
- Chronic exposure increases the number of melanosomes (organelles in melanocytes which contain melanin) and their transfer to the surrounding keratinocytes
Contributors:
Dr Christophe HSU – dermatologist. Geneva, Switzerland
Source of information: Handog E. Brown Spots: Melasma Updates.2012 (02) – 20th Regional Conference of Dermatology (RCD) – Manila, Phillipines
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