This chapter describes the physical characteristics, medical complications, and 
cognitive and psychological profiles that are associated with chromosomal 
aneuploidy conditions, a group of conditions in which individuals are born with 
one or more additional chromosome. Overall, chromosomal aneuploidy conditions 
occur in approximately 1 in 250 children. Information regarding autosomal 
disorders including trisomy 21 (Down syndrome), trisomy 13 (Patau syndrome), and 
trisomy 18 (Edward syndrome) are presented. Sex chromosome aneuploidy conditions 
such as Klinefelter syndrome (47,XXY), XYY, trisomy X, and Turner syndrome 
(45,X), in addition to less frequently occurring tetrasomy and pentasomy 
conditions are also covered. Treatment recommendations and suggestions for 
future research directions are discussed.