What Is Cat Eye Syndrome?

People with cat eye syndrome have a very distinctive look

Close up of woman's eye.
Credit: Dougal Waters/Digital Vision/Getty Images

Cat eye syndrome (CES, also known as Schmid–Fraccaro syndrome, is a condition caused by a chromosomal abnormality and is named after the cat-like eye shape it causes. CES is the result of a genetic defect in chromosome 22, resulting in an extra chromosome fragment.

Cat eye syndrome affects both males and females and is estimated to occur in 1 in 74,000 individuals. If you have CES, you are most likely the only one in your family to have the condition since it is a chromosomal abnormality as opposed to a gene.

Symptoms of Cat Eye Syndrome

If you or your child has CES, you may experience a wide range of symptoms. About 41 percent of individuals with cat eye syndrome have the following three symptoms in common:

  • Absence of tissue from the colored part of one or both eyes (iris coloboma)
  • Small growths of skin (tags) or depressions in the skin (pits) of the outer ears
  • An absence or obstruction of the anus (anal atresia)

Other, more common, symptoms of Schmid–Fraccaro syndrome include congenital heart defects, downward slanting openings between the upper and lower eyelids, defects of the urinary tract or kidneys, short stature, and a cleft palate. There are other less common birth defects, which have been noted as part of the condition, too. 

What Causes Cat Eye Syndrome?

According to the National Organization for Rare Disorders (NORD), the exact cause of cat eye syndrome is not fully understood. In some cases, the chromosomal abnormality appears to arise randomly due to an error in the division of the parent’s reproductive cells.

In these cases, your parent has normal chromosomes. In others, it may appear to result from a balanced translocation in one of your parents.

Translocations occur when portions of certain chromosomes break off and are rearranged, resulting in shifting of genetic material and an altered set of chromosomes.

If a chromosomal rearrangement is balanced—meaning that it consists of an altered but balanced set of genes—it is usually harmless to the carrier. However, if you have CES, your chromosomal rearrangement may increase your risk of passing down your abnormal chromosomal development to your children.

In other cases, a parent of an affected child may have the marker chromosome in some body cells and, in some instances, manifest certain, possibly mild features of the disorder. Evidence indicates that this chromosomal abnormality may be transmitted through several generations in some families; however, as noted above, expression of associated features may be variable. As a result, only those with multiple or severe features may be identified.

Some researchers suggest that certain regions of the chromosome are susceptible to chromosomal instability and chromosomal rearrangements associated with certain congenital malformation disorders, including cat eye syndrome. Such investigators indicate that the basic underlying defect for the syndrome may be inherited fragile chromosomal sites or other possible predispositions that may lead to complex rearrangements seen in cat eye syndrome.

Chromosomal analysis and genetic counseling may be recommended for parents of an affected child to help confirm or exclude the presence of certain abnormalities involving chromosome 22 and evaluate recurrence risk.

Diagnosing and Treating Schmid–Fraccaro Syndrome

Since cat eye syndrome is inherited, if you have the syndrome, that means you were born with it. Typically, your doctor will diagnose you or your child based on the symptoms they have. Genetic testing, such as a karyotype, can confirm the presence of the specific genetic defect in chromosome 22—tripling or quadrupling of parts of the chromosome—that is associated with CES.

How CES is treated is based on the symptoms you or your child has. Some children may need surgery to repair birth defects in their anus or heart. Most people with cat eye syndrome have an average life expectancy unless they have life-threatening physical problems such as a severe heart defect.


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