Down Syndrome

Down Syndrome

About Down Syndrome

Down syndrome or Down's syndrome, also known as trisomy 21, is a chromosomal condition caused by the presence of all or part of a third copy of chromosome 21. It is named after John Langdon Down, the British physician who described the syndrome in 1866. The condition was clinically described earlier in the 19th century by Jean Etienne Dominique Esquirol in 1838 and Edouard Seguin in 1844. Down syndrome was identified as a chromosome 21 trisomy by Dr. Jerome Lejeune in 1959. Down syndrome can be identified in a baby at birth, or by prenatal screening. The CDC estimates that about one of every 691 babies born in the United States each year is born with Down syndrome. Down syndrome occurs in all human populations, and analogous conditions have been found in other species such as chimpanzees. Often Down syndrome is associated with a delay in cognitive ability and physical growth, and a particular set of facial characteristics.

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