Cat eye syndrome is a rare human disease that is caused by a chromosomal abnormality. It is included within the aneuploidies, or diseases in which the number of chromosomes is altered. It is characterized by the existence of 3 or 4 copies of a fragment of chromosome 22 (22q11.2). In a normal cell there are 2 copies of each of the chromosomes, the diseases in which a chromosome is tripled are called trisomies and when they are quadrupled they are called tetrasomies. The cat eye syndrome may correspond to a trisomy or tetrasomy.
In affected patients, a series of malformations that affect various organs are present from the moment of birth. These include the existence of ocular coloboma from which the name of the condition comes, as well as anal atresia, malformations of the heart and kidneys, characteristic facial appearance and mental retardation. There is great variability in the manifestations and their severity. There is one case for every 74,000 births, which is why it is considered a rare disease.
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