What is cat eye syndrome?

Cat eye syndrome is a genetic disorder which is considered a rare disease due to its low prevalence, affecting less than 1 in 150,000 newborns and men and women equally.

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 eye shape very characteristic. But beyond the eyes, the truth is that defects and symptoms that it can produce are very varied.

There are people who can have a very serious affectation, while others only develop mild symptoms.

What is its cause?

All human beings, if there is no chromosome alteration, have 23 pairs of chromosomes in the cells of their body. Each chromosome has a narrowing that divides it into two regions known as chromosome arms: short arm, called "p" and long arm called "q".

In cat eye syndrome there is a small extra chromosome which is composed of a segment of the upper half of the short arm of the chromosome 22, called ter, and a small region of the long arm, the q11 region of chromosome 22. With these alterations we have the genetic abnormality associated with this syndrome that is simplified into 22pter-22q11.

This extra chromosome 22 is present three times (trisomy) or four times (tetrasomy), instead of twice. In some cases, this anomaly is only present in some cells of some tissues and not in the whole organism, which gives it the name of mosaicism. In this disease, being mosaic of cat eye syndrome does not imply that the child has milder symptoms or complications. A small portion of the 22q11 region is responsible for most of the features associated with cat eye syndrome. This region is known as the "critical region of cat eye syndrome" and contains approximately 12 genes.

In most cases there are no other people in the family, that is, it is not hereditary.

Abnormalities and symptoms associated with cat eye syndrome

The signs and symptoms are highly variable and none of the features are always present. Only 41% of children with cat eye syndrome present a classic combination of anomalies characterized by coloboma of the iris, anal anomalies, and anomalies in the region located in front of the ears (pre-atrial).

The symptoms and signs of this syndrome can be very varied and can include:

Eye abnormalities

They may include abnormalities of the iris of the eye such as iris colobomas. This type of malformation is holes in the iris of the eye that can look like a second pupil or black groove at the edge of the pupil, giving it an appearance similar to that of a feline eye. It is the sign that gives the name to this syndrome. They can also present:

• Coloboma of the retina (layer that lines the back of the eye)
• Increased space between the eyes (hypertelorism)
• Inclined eyelid fences for bass
• Choroidal coloboma
• Abnormally very small eyes (microphthalmia).

Other anomalies

• Ear abnormalities: ears with low implantation, presence of pre-auricular alterations such as skin folds in front of the ear (90% of cases) and presence of depression in the skin in the region in front of the ear. It can be associated. • Craniofacial malformations: They may present with facial dysmorphia, micrognathia (very small jaw) and. • Anal malformations: as narrowing or closing of the anal opening. This is called anal atresia. • Genital abnormalities: abnormal communication between genitalia and urinary bladder or urogenital fistula or absence of uterus. • Kidney abnormalities: small kidneys, of abnormal location of the kidney or absence of the kidney. This is called renal agenesis. • Bone abnormalities: in the hip, ribs or absence of the radius. • Cognitive deficit or moderate intellectual disability. • Uterine growth retardation. • Malformation of the heart. • Digestive malformations: such as biliary atresia or intestinal malrotation. • Diminution muscle tone • Short stature. • Biliary atresia: obstruction of the drainage system (biliary tree) from the liver to the intestine.

How is it diagnosed

If there are suspicions in the examination of the child that he may have this syndrome, the. This is called performing a karyotype that will show the presence of the extra chromosome 22.

In some cases, cat eye syndrome can be diagnosed prenatally, before birth. If suspicious features are seen on ultrasound during pregnancy, tests such as chorionic villus samples may be ordered to confirm the diagnosis.

Prognosis and treatment

The prognosis depends on the severity of the symptoms that occur, but in most cases patients have a good forecast with a normal life expectancy. The most serious abnormalities can be the most severe cardiac, anal or kidney abnormalities. Treatment depends on the symptoms and malformations that present and each case must be evaluated individually and treated in a multidisciplinary way.

• Its colloquial name is due to the fact that the people who suffer from it have a very characteristic eye shape. 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, while others only develop mild symptoms. The most serious abnormalities can be the most severe cardiac, anal or kidney abnormalities.
• The prognosis depends on the severity of the symptoms that occur, but in most cases patients have a good prognosis with a normal life expectancy.