Abstract:Non-syndromic microtia is mainly manifested as external and middle ear deformity.It is usually not associated with other parts of the deformity, and most cases are sporadic. Some scholars believe that non-syndromic microtia is the second largest craniofacial congenital deformity in China. It may be one of the milder clinical manifestations of hemifacial microsomia. Hemifacial short deformity is often caused by the first and second gill arch hypoplasia. Although a lot of literature on non-syndromic microtia with familial aggregation and partial genetic variants have been reported. However, this does not explain most of the phenotypes of non-syndromic microtia, which is still developed by individuals with genetic predisposition in specific environments. It has been reported that retinoic acid, thalidomide, mycophenolate and immunosuppressive drugs can cause nonsyndromic microtia. The mechanism may be related to the disturbance of neural crest cell migration and local vascular rupture. Therefore, the paper will introduce the neural crest cell hypothesis and vascular rupture hypothesis to explain the non-syndromic microtia.
