Cat Eye Syndrome
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Cat-eye syndrome (CES) or Schmid–Fraccaro syndrome is a rare condition caused by an abnormal extra
chromosome A chromosome is a package of DNA containing part or all of the genetic material of an organism. In most chromosomes, the very long thin DNA fibers are coated with nucleosome-forming packaging proteins; in eukaryotic cells, the most import ...
, i.e. a
small supernumerary marker chromosome A small supernumerary marker chromosome (sSMC) is an abnormal extra chromosome. It contains copies of parts of one or more normal chromosomes and like normal chromosomes is located in the cell's nucleus, is replicated and distributed into each d ...
. This chromosome consists of the entire short arm and a small section of the long arm of
chromosome 22 Chromosome 22 is one of the 23 pairs of chromosomes in human cells. Humans normally have two copies of chromosome 22 in each cell. Chromosome 22 is the second smallest human chromosome, spanning about 51 million DNA base pairs and representing b ...
. In consequence, individuals with the cat-eye syndrome have three ( trisomic) or four ( tetrasomic) copies of the genetic material contained in the abnormal chromosome instead of the normal two copies. The prognosis for patients with CES varies depending on the severity of the condition and their associated signs and symptoms, especially when heart or kidney abnormalities are seen.


Signs and symptoms

* Unilateral or bilateral iris
coloboma A coloboma (from the Greek , meaning "defect") is a hole in one of the structures of the eye, such as the iris, retina, choroid, or optic disc. The hole is present from birth and can be caused when a gap called the choroid fissure, which is ...
(absence of tissue from the colored part of the eyes) * Preauricular pits/tags (small depressions/growths of skin on the outer ears) * Anal atresia (abnormal obstruction of the anus) * Downward-slanting
palpebral fissures The palpebral fissure is the elliptic space between the medial and lateral canthi of the two open eyelids. In simple terms, it is the opening between the eyelids. In adult humans, this measures about 10 mm vertically and 30 mm horizontally. Var ...
(openings between the upper and lower eyelids) *
Cleft palate A cleft lip contains an opening in the upper lip that may extend into the nose. The opening may be on one side, both sides, or in the middle. A cleft palate occurs when the palate (the roof of the mouth) contains an opening into the nose. The ...
* Kidney problems (missing, extra, or underdeveloped kidneys) * Short stature *
Scoliosis Scoliosis (: scolioses) is a condition in which a person's Vertebral column, spine has an irregular curve in the coronal plane. The curve is usually S- or C-shaped over three dimensions. In some, the degree of curve is stable, while in others ...
/skeletal problems * Cardiac defects (such as TAPVR) * Micrognathia (smaller jaw) *
Hernia A hernia (: hernias or herniae, from Latin, meaning 'rupture') is the abnormal exit of tissue or an organ (anatomy), organ, such as the bowel, through the wall of the cavity in which it normally resides. The term is also used for the normal Devel ...
s * Biliary atresia * Rarer malformations can affect almost any organ *
Intellectual disability Intellectual disability (ID), also known as general learning disability (in the United Kingdom), and formerly mental retardation (in the United States), Rosa's Law, Pub. L. 111-256124 Stat. 2643(2010).Archive is a generalized neurodevelopmental ...
– many are intellectually normal; about 30% of CES patients have moderately impaired mental development, although severe intellectual disability is rare. The term "cat eye" syndrome was coined because of the particular appearance of the vertical colobomas in the eyes of some patients, but over half of the CES patients in the literature do not present with this trait.


Genetics

The small supernumerary marker chromosome (sSMC) in CES usually arises spontaneously. It may be hereditary and parents may be mosaic for the marker chromosome, but show no
phenotypic In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...
symptoms Signs and symptoms are diagnostic indications of an illness, injury, or condition. Signs are objective and externally observable; symptoms are a person's reported subjective experiences. A sign for example may be a higher or lower temperature ...
of the
syndrome A syndrome is a set of medical signs and symptoms which are correlated with each other and often associated with a particular disease or disorder. The word derives from the Greek language, Greek σύνδρομον, meaning "concurrence". When a sy ...
. This sSMC may be small, large, or ring-shaped, and typically includes 2 Mb, i.e. 2 million DNA
base pairs A base pair (bp) is a fundamental unit of double-stranded nucleic acids consisting of two nucleobases bound to each other by hydrogen bonds. They form the building blocks of the DNA double helix and contribute to the folded structure of both DNA ...
, termed the CES critical region, located on its q arm(s) between its
band Band or BAND may refer to: Places *Bánd, a village in Hungary * Band, Iran, a village in Urmia County, West Azerbaijan Province, Iran * Band, Mureș, a commune in Romania * Band-e Majid Khan, a village in Bukan County, West Azerbaijan Province, ...
11 and terminus (area notated as 22pter→q11)(also see small supernumerary marker chromosomes in cat eye syndrome). This area contains the '' CECR1'', ''SLC25A18'', and '' ATP6V1E1'' genes which are strong candidate genes for causing or promoting at least some of the birth defects in CES.


Diagnosis

An ultrasound exam may be used by a doctor to detect a birth defect that might be CES before a baby is born. An ultrasound creates an image of the fetus using sound waves. It might uncover specific CES-specific flaws. A follow-up test, like an amniocentesis, may be ordered by the doctor if they see these characteristics on an ultrasound. The doctor collects an amniotic fluid sample for analysis during amniocentesis. Extra chromosomal material from chromosome 22q11 helps doctors identify CES. The diagnosis can be verified through
genetic testing Genetic testing, also known as DNA testing, is used to identify changes in DNA sequence or chromosome structure. Genetic testing can also include measuring the results of genetic changes, such as RNA analysis as an output of gene expression, or ...
. These tests could consist of: * Karyotyping. A picture of a person's chromosomes is generated by this test. * FISH, or fluorescence in situ hybridization. It is able to identify and pinpoint a particular DNA sequence on a chromosome. The healthcare provider will likely order more testing when CES is identified to look for any potential extra problems, like heart or kidney disorders. These tests may include: * X-rays and other imaging tests * electrocardiography (EKG) * echocardiography * eye examination * hearing tests * cognitive function tests


History

The abnormalities common to CES were first cataloged in 1899, and described in association with a small marker chromosome in 1965. Early reports of CES discuss the possibility of chromosome 13 involvement. Now, CES is considered to be present with the chromosome 22 trisomy findings.


See also

* Trisomy 22


References


External links

{{Authority control Congenital disorders Syndromes affecting stature Syndromes affecting the jaw Syndromes affecting the heart Syndromes affecting the kidneys Syndromes with cleft lip and/or palate Syndromes affecting the eye Rare syndromes