牙釉质是由外胚层，晶状体是由表面外胚层发育形成。外胚层发育异常，可表现为无牙或部分无牙，亦可伴有晶状体的畸形。患者蔡某，女，17岁。因多数牙缺失要求修复。自幼视力差，但无发热及外伤史。患者为第一胎．10个月顺产。母孕期曾4次跌伤，未服激素及其它药，亦无感染史。 Enamel is composed of ectoderm, the lens is formed by the development of surface ectoderm. Ectodermal dysplasia, can be expressed as no tooth or part of the toothless, can also be associated with lens deformities. Patient Cai, female, 17 years old. Due to the loss of most teeth required repair. Poor vision since childhood, but no history of fever and trauma. The patient is the first child. 10 months of birth. During pregnancy, she fell 4 times and failed to take hormones and other drugs. She also had no history of infection.