Definition, etiology, pathogenesis and clinical manifestations of melasma I. Definition: Melasma is a hyperpigmented skin disease mostly found in the face of young and middle-aged women. Etiology and mechanism: UV radiation, cosmetics, pregnancy, endocrine disorders, drugs (such as birth control pills, chlorpromazine, phenytoin sodium, etc.), imbalance of trace elements, etc. can cause chloasma, where pregnancy is also known as gestational spots, and estrogen levels are elevated, and can disappear after delivery; certain chronic diseases (such as gynecological diseases, hepatitis, chronic alcoholism, hyperthyroidism, tuberculosis, visceral tumors, etc.) Certain chronic diseases (such as gynecological diseases, hepatitis, chronic alcoholism, hyperthyroidism, tuberculosis, internal tumors, etc.) can also occur; the occurrence of this disease may also be affected by genetic factors. Linyi People’s Hospital, Department of Dermatology, Wang Shouzhong Third, clinical manifestations: more accumulation of young and middle-aged women, men can also occur. It is often aggravated in spring and summer, and reduced in autumn and winter. The butterfly type occurs symmetrically on the cheekbones and cheeks of the face, and can also involve the forehead, nose and mouth. Typical lesions are yellowish brown or dark brown patches, varying in size, with clear edges. There are no conscious symptoms. The duration of the disease is variable and may last for several months or years.