2.1.3.3　Pigmentation related diseases

Skin pigmentation is subject to many physiological and external conditions.Genetic factors，long-term exposure to ultraviolet，and elevated estrogen levels are common causes of chloasma.In addition，it has also been found that the increase in the number of dermal resident cells，mast cells，fibroblasts and dermal blood vessels is related to chloasma pigmentation.miRNAs has a potential role in the generation of melanin in chloasma and the transfer of melanosome.With age，local skin pigmentation may appear age spots.Some skin diseases can cause located post-inflammatory pigmentation，such as acne，atopic dermatitis and lichen planus.Endocrine diseases such as primary adrenal insufficiency can also cause skin pigmentation.Skin melanin production disorder or deficiency can also lead to diseases，such as acquired depigmentation skin and mucous membrane disease，vitiligo and congenital pigmentation disorder，albinism.(https://www.daowen.com)