Blue sclera is caused by the thinning of the sclera, which cannot effectively hide the brownish-black choroid in the eye, making it light blue when viewed under natural light. There are many diseases that cause blue sclera, and the following are the specific diseases introduced. 1.Rubinstein-Taybi’s syndrome Blue sclera is an external manifestation of Rubinstein-Taybi’s syndrome. The symptoms of Rubinstein-Taybi’s syndrome include short thick thumb, mental developmental disorder, high mouth cover and other idiosyncratic appearance. The presentation is characterized by delayed psychomotor development and a history of respiratory tract infections. The face has varying degrees of high brow arches, low sloping lid fissures, drooping lids, occasional inner lid redundancy, protruding eyes, strabismus, blue sclera, wide nasal bridge, long nasal diaphragm, underdeveloped upper jaw, abnormal size, shape and position of the ears, high bowed palate, and short thick thumbs (toes). 2.Hallerman-Streiff’s syndrome Hallerman-Streiff’s syndrome has cranial hypoplasia with congenital cataract and hair thinning, blue sclera, corneal malformation. x-ray shows hypoplasia of the lower jaw, temporal joint forward displacement, condyles can be completely absent. 3.VanDerHoeve syndrome VanDerHoeve syndrome also has blue sclera phenomenon, which is characterized by three major features: brittle bone, blue sclera and deafness, and is accompanied by ligamentous laxity and dental changes. In addition to VanDerHoeve syndrome, blue sclera is also seen in genetic diseases of other systems, such as Marfan’s syndrome and E-D syndrome.