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Also known by the term Schmid-Fraccaro syndrome, cat eye syndrome is a rare condition. A type of genetic disorder, the chromosome abnormality can affect the eyes, ears, kidneys and heart   . The condition is caused by the short arm (p) and a small section of the long arm (q) of human chromosome 22.
Generally, chromosome 22 is found twice in the human body. But in individuals with cat eye syndrome, the chromosomes are present thrice (trisomic) or four times (tetrasomic). The name cat eye syndrome was derived from the fact that the eyes of the individual with the condition looks like that of a cat's; as it causes the development of a hole in the iris .
The chromosome abnormality occurs only to 1 in 75,000 people  . In most cases, the condition develops sporadically and is not necessarily linked with genetics. In some individuals, the condition can also cause a defect called coloboma which affects the pupil. The signs and symptoms of the condition vary from one individual to the other. That is, some may experience mild to no symptoms at all whereas others may experience a range of severe symptoms .
Symptoms Of Cat Eye Syndrome
The congenital disorder can affect both men and women. The various symptoms of cat eye syndrome include the following :
- Skin tags or pits in front of the ears (small pieces of hanging skin)
- Urinary tract problems
- Anal atresia (no opening for anus)
- Hearing loss
- Unusually shaped ears
- Congenital heart defects
- Hypertelorism (widely spaced eyes)
- Downward slanting palpebral fissures (outside corners of the eyes point downward)
- Strabismus (crossed eyes)
- Cleft lip or palate 
- Reproductive tract defects, such as underdevelopment of the uterus (females), absence of the vagina (females), or testes (males)
- Developmental delays
- Intellectual disability (mild/moderate)
- Skeletal abnormalities (curved spine, fused vertebrae, missing ribs, or dislocated hips)
- Iris coloboma
The symptoms can also appear in the infant during birth. The infant can be born with the following symptoms  .
- Problems with vision
- Hearing trouble
- Kidney problems
- Speech problems
Causes Of Cat Eye Syndrome
The genetic disorder is developed as a result of a defect in an individual's chromosomes. An inverted duplicate chromosome 22 is asserted as being the cause of cat eye syndrome. The extra genetic material or the chromosome causes the development of the signs and symptoms such as anal atresia, speech problems, coloboma  etc.
The exact reason as to why cat eye syndrome is developed in a person is still unclear. According to the NORD (National Organization for Rare Disorders), the exact cause of the abnormality still poses uncertainty  .
In some rare cases, cat eye syndrome develops due to an error in the division of the parent's reproductive cells. It can also develop due to translocation in the parent. That is when an individual's body with the syndrome undergoes translocation  (when portions of certain chromosomes break off and are rearranged - which causes the shifting of genetic material and altered set of chromosomes), there is a possibility of passing down the chromosome with abnormal development to the unborn child. Commonly, the chromosomes appear randomly  .
Diagnosis Of Cat Eye Syndrome
The doctor will be, in most cases, able to recognise the development of the defect in the child during an ultrasound test. As cat eye syndrome is developed from birth, the doctor may be able to detect the characteristics of the condition using the sound waves .
If any characteristic of the condition is revealed during the ultrasound, the doctor will ask to do a follow-up test called amniocentesis. Amniocentesis will involve extracting a sample of amniotic fluid, so as to examine and analyse the possibility of cat eye syndrome.
2. Genetic testing
The doctors can detect the presence of the additional chromosome with the help of genetic testing. If any defect is detected, the doctor will take a sample of the placenta through your vagina or your abdomen using a catheter; to be send to a specialist for further testing.
Under this process, the doctors use the following types of testing to analyse the presence of the extra chromosome.
Fluorescence in situ hybridization or FISH - This method will help in detecting as well as locating specific DNA sequences within a chromosome  .
Karyotyping - This process helps in procuring an image of the individual's chromosomes. Thereby aiding the doctor in examining the possible occurrence of any defects  .
Once the above-mentioned diagnosis is carried out, the doctor will be able to understand and assess the possible development of cat eye syndrome. Apart from the two methods, the doctor may ask you to carry out some more tests to detect any other defects or abnormalities (such as a kidney or heart defect)  .
The additional tests are mentioned below .
- Hearing tests
- Eye examination
- Electrocardiography (EKG)
- Cognitive function tests
- X-rays and other imaging tests
Treatment For Cat Eye Syndrome
The genetic disorder is not a temporary change but a permanent change to the chromosome. With the condition being a congenital disorder, there is no cure for cat eye syndrome as of now. However, some of the symptoms of the condition can be treated. The treatment plan to be adopted for cat eye syndrome is entirely dependent on the symptoms of the individual .
The treatment plan for cat eye syndrome involves a group of medical practitioners. The team will include 
- gastrointestinal specialists,
- heart specialists or cardiologists, and
- eye specialists.
As there is no cure for the condition as a whole, the treatments will be focused on the symptoms, specifically. The treatment will include 
- surgery to correct anal atresia, hernias, genital defects, skeletal abnormalities, and other physical issues,
- speech therapy,
- occupational therapy,
- physical therapy,
- special education for those with intellectual disabilities, and
- growth hormone therapy for people with short stature.
Complications Of Cat Eye Syndrome
An individual suffering from the condition can fall victim to various difficulties. Some of the complications posed by cat eye syndrome are 
- hearing defects,
- mental health deficiencies,
- vision defects,
- gastrointestinal or kidney defects,
- cardiovascular abnormalities, and
- risk of developing infections from surgical procedures.
Cat eye syndrome is not necessarily life-threatening. However, infants who are born with severe signs such as anal atresia or heart and kidney problems are most likely to pass away. This is due to the inability of their body to respond to the treatment methods. Therefore, the life expectancy of people with cat eye syndrome varies, depending on the severity of the symptoms  .
In most cases, the condition does not reduce the life expectancy of an individual. If you desire to become pregnant, it is best to consult with a genetic counsellor so as to go over the possible complications the condition can cause, including the possibility of passing down the condition on to the infant.
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