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Cat Eye Syndrome. By : Amy C 4 th block. Chromosome 22.
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Cat Eye Syndrome By : Amy C 4th block
Chromosome 22 • Chromosome 22 is the second smallest of the human autosomes. The short arm (22p) contains a series of tandem repeat structures including the array of genes that encode the structural RNAs of the ribosomes, and is highly similar to the short arms of chromosomes 13, 14, 15 and 21. The long arm (22q) is the portion of human chromosome 22 that contains the protein coding genes and this is the region that has now been sequenced. The completed sequence consisted of 12 contiguous segments covering 33.4 million bps separated by 11 gaps of known size.
What is Cat Eye Syndrome? • Cat eye syndrome is a rare chromosomal disorder that may be evident at birth. Individuals with a normal chromosomal make-up have two 22nd chromosomes, both of which have a short arm, known as 22p, and a long arm, called 22q. However, in individuals with cat eye syndrome, the short arm and a small region of the long arm of chromosome 22 (i.e., 22pter-22q11) are present three or four times (trisomy or tetrasomy) rather than twice in cells of the body.
Where does Cat Eye Syndrome come from? • The name "cat eye syndrome" is derived from a distinctive eye (ocular) abnormality that is present in some affected individuals. This feature consists of partial absence of ocular tissue (coloboma), often affecting both eyes (bilateral). Affected ocular tissues may include the colored region (iris), the middle layer (choroid), and/or the nerve-rich innermost membrane (retina) of the eye.
What does Cat Eye Syndrome cause? • Symptoms and findings may vary greatly in range and severity, including among affected members of the same family. While some may have few or mild manifestations that may remain unrecognized, others may have the full spectrum of malformations. However, in many cases, characteristic features of the disorder include mild growth delays before birth; mild mental deficiency; and malformations of the skull and facial (craniofacial) region, the heart, the kidneys, and/or the anal region.
What are some of the other leading causes of Cat Eye Syndrome? • Individuals with cat eye syndrome frequently have coloboma(s), downslanting eyelid folds (palpebral fissures), widely spaced eyes (ocular hypertelorism), and/or other ocular defects; misshapen ears with abnormal outgrowths of skin and small depressions in front of the outer ears (preauricular tags and pits); and/or absence (atresia) of the anal canal, with an abnormal passage (fistula) from the end portion of the large intestine (rectum) into abnormal locations (e.g., the bladder, vagina, or perineum). Additional features may commonly include variable congenital heart (cardiac) defects, kidney (renal) abnormalities, skeletal defects, and/or other physical findings.
When was the first case of Cat Eye Syndrome reported? • The additional chromosome 22 generally arises de novo from one of the parents. Since CES is a rare chromosome disorder in which transmission is possible through both sexes, chromosome examination should be performed if one of the parents displays characteristic features such as a preauricular pit or downslanting palpebral fissures. Even in nonsymptomatic parents, mosaicism for an extra chromosome is possible. The earliest transmission was reported by Schachenmann et al. (1965)
Related causes of Cat Eye Syndrome • A female with a severe form of CES associated with a molecular type II chromosome. At birth, she had severe craniofacial abnormalities, including microcephaly, total absence of the external ears bilaterally, hypertelorism with downslanting palpebral fissures, bilateral coloboma of the iris, flat nasal bridge with prominent nose, thin upper lip, and micrognathia. Other features included anal stenosis, patent ductus arteriosus, and intra- and extrahepatic biliary atresia. She died at age 1 month of cardiac failure. Cytogenetic analysis showed a small de novo extra chromosome in all cells with a karyotype of 47,XX, +idic(22)(pter-q11.2::q11.2-pter) with the duplication breakpoints distal to 22q11.2. The marker could be classified as CES type II symmetrical.
Cat Eye Syndrome • Cat Eye Syndrome can sometimes be fatal. • However, most cases are only a disorder that a person can live with.
References • www.google.com.12/11/06 • www.chromosomes.com12/12/06 • www.diseases.com12/13/06 • www.galileo.com12/13/06
