Update in the etiology and pathogenesis of chloasma

Chloasma is a common acquired hyperpigmentary disorder mainly occurring in women of reproductive age,It usually appears as hyperpigmented maculae and patches symmetrically distributed on the face.Chloasma is often difficult to treat and has a significant negative impact on patients' quality of life.Although its etiology and pathogenesis remain unclear,it has been known that the development of chloasma is associated with photodamage,ahnormality in hormone levels and in distribution of their receptors,genetic factors,free radicals,vascular endothelial function and blood rheology,skin microflora imbalance,psychological factors,certain diseases,and so on.Of these associated factors,photodamage and abnormality in hormone levels and in distribution of their receptors are recognized as the most important. Key words: Chloasma ;  Ultraviolet ;  Estrogens ;  Heredity ;