Overview of chromosomal deletion syndromes

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Chromosomal deletion syndromes occur when part of a chromosome is missing.
(See also Overview of Chromosome Disorders.)
Chromosomes are structures within cells that contain DNA and many genes.
A gene is a segment of deoxyribonucleic acid (DNA) and contains the code for a specific protein that functions in one or more types of cells in the body (see Genes and Chromosomes for a discussion about genetics). Genes contain instructions that determine how the body is supposed to function.
When parts of chromosomes are missing, a number of syndromes can occur. These syndromes are called chromosomal deletion syndromes. They tend to cause birth defects and limited intellectual development and physical development. In some cases, defects can be severe and affected children die during infancy or childhood.
There are many chromosomal deletion syndromes, which include

Cri-du-chat syndrome
Prader-Willi syndrome
Wolf-Hirschhorn syndrome

Chromosomal deletions can be suspected before or after birth and confirmed by chromosomal testing.
Some physical defects can be corrected with surgery, but generally treatment is supportive.