Cat eye syndrome: what does it consist of?

Cat eye syndrome is a genetic disorder that it is considered a rare disease due to its low prevalence. It is also called Schmid-Fraccaro syndrome, since these scientists were the first to describe it.

Its colloquial name is due to the fact that people who suffer from it have a very characteristic eye shape. This disorder is usually diagnosed at birth. But beyond the eyes, the truth is that the defects and symptoms that it can produce are very varied.

There are people who can have a very serious affectation, as well as others who only develop mild symptoms. In this article we explain everything you need to know about cat eye syndrome and what its implications are.

What is cat eye syndrome?

Cat eye syndrome, he explains Orphanet, it is a rare disease. This is because its prevalence is low, below 1 in 150,000 newborns, affecting men and women equally.

Its direct cause is an abnormality in a chromosome. Chromosomes are the structures that contain genetic information. Normally, humans have 23 pairs of chromosomes. Each of them is made up of two arms: a short one, called an arm p, and a long one called arm what.

What happens in cat eye syndrome is that these patients have two short arms on the same chromosome 22. That is, it is as if there is a little extra chromosome 22. This is what triggers a series of developmental abnormalities. It is not known exactly why this happens. What is known is that it is not usually inherited.

The parts of the body that are most affected in this disease are the eyes, ears, heart, anal region and kidneys. However, as we pointed out at the beginning, gravity is highly variable.

The characteristic sign is an anomaly called coloboma. It consists of a ragged pupil or a second pupil appearing in the iris. That is why it is called ‘cat eye syndrome’.

The disease is considered rare and chromosomal, since the alteration of the chromosomes is very rare.

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What symptoms does it present?

As we have noted, the symptoms and severity of cat eye syndrome are heterogeneous. As explained Genetic and Rare Diseases Information Center, only 41% of people have a classic combination of abnormalities.

This classic combination to which they refer includes the coloboma of the iris, kidney disorders and those in the area of ​​the ears. These are usually ears that are lower than normal. and that present a fold just in front.

The kidneys tend to be small, and in some cases they may be in the wrong place. Some patients even have only one of the kidneys, which can affect the quality of life. This is explained in an article published in the Spanish Association of Pediatrics.

It is also important to note that, with regard to the perianal area, atresia of the anus may appear. It is a defect that consists in that the anus is not perforated. That is, there is no communication between the rectum and the exterior because the skin is intact.

Coloboma is present in more than 50% of cases. In addition, these people may have eyes that are wider than normal or small. In principle, vision need not be affected, although it can lead to cataracts.

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Other symptoms of cat eye syndrome

People with cat eye syndrome are usually short. Bone tissues tend to be abnormal and, in some cases, certain bones do not even develop. For example, the radius, which is part of the forearm.

Intellectual disability is common, but moderate. That is, they are people who require supervision both in learning and at work. However, through therapies they can achieve some autonomy.

The heart can also be affected. According to a study carried out at the University of Antioquia, it is typical that there are cardiac malformations such as persistent ductus or interatrial communication. Other symptoms that may appear are the following:

  • Decreased muscle tone
  • Genital abnormalities, such as abnormal communication with the urinary bladder. In women there may also be an absence of the uterus.
  • There may be intestinal malrotation or biliary atresia. Malrotation is that part of the intestine is in a different place than normal. Atresia makes bile unable to pass from the gallbladder to the intestine.
  • Some have a very small jaw or sunken lip.
  • Hearing decreases.

Diagnosis of cat eye syndrome

The diagnosis of cat eye syndrome is made at birth and even earlier. Prenatal diagnostic techniques have evolved remarkably. Thanks to them, the risk of the fetus suffering a chromosomal abnormality can be calculated.

In the event that it is not diagnosed during pregnancy, this syndrome becomes evident at birth. As we have explained, the appearance is usually characteristic. Especially the shape of the ears and eyes.

To confirm the diagnosis, two complementary tests can generally be performed. One of them is the karyotype. It allows you to examine the size, number, and shape of chromosomes. With it, the presence of an alteration of chromosome 22 is evidenced.

The other test is fluorescent in situ hybridization (FISH). It is a complex technique that makes it possible to locate a specific DNA sequence on a chromosome. This is how you see the specific defect.

In addition to the basic diagnosis, People with cat eye syndrome often require many other tests to check which organs are affected. The echocardiogram and electrocardiogram are essential, as well as x-rays.

The karyotype test confirms the existence of the syndrome.

How is this pathology treated?

The truth is there is no specific treatment for cat eye syndrome. However, most people who have it have a good prognosis. This depends on the severity of the involvement, but many of the defects can be corrected thanks to current therapeutic options.

What we must remember is that this syndrome, beyond producing characteristic eyes, can affect many other parts of the body. It is a chromosomal defect that causes alterations in appearance, in the digestive system and on an intellectual level. Therefore, its approach does not depend on a single specialty.

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