Cat Eye Syndrome Symptoms and Causes

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, which causes an extra chromosome fragment.

A woman's blue eye in the daylight
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Incidence of Cat Eye Syndrome

Cat eye syndrome affects both males and females and is estimated to occur in one in 50,000 to one in 150,000 individuals. If you have CES, you are most likely the only one in your family to have the condition since it's a chromosomal abnormality as opposed to a gene.


If you or your child has CES, you may experience a wide range of symptoms. About 80 to 99% of individuals with cat eye syndrome have the following three symptoms in common:

  • Small growths of skin (tags) of the outer ears
  • 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 includes:

  • The absence of tissue from the colored part of one or both eyes (iris coloboma)
  • Congenital heart defects
  • Rib abnormalities
  • Downward slanting openings between the upper and lower eyelids
  • Defects of the urinary tract or kidneys
  • Short stature
  • Cleft palate
  • Wide-set eyes
  • Intellectual disability

There are other less common birth defects, which have been noted as part of the condition, too.


According to the National Organization for Rare Disorders (NORD), the exact cause of cat eye syndrome is not entirely understood. In some cases, the chromosomal abnormality appears to arise randomly due to an error in how a parent’s reproductive cells divide. In these cases, your parent has normal chromosomes. In other cases, it appears 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 even exchange of genetic material with no genetic information extra or missing—it's usually harmless to the carrier.

It's very rare, but carriers of a balanced translocation may have a slight risk of passing down a chromosomal abnormality to their children.

In other rare cases, a parent of an affected child may have the marker chromosome in some of the 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, the expression of associated features may be variable. As a result, only those with multiple or severe features may be identified.

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 to evaluate recurrence risk.

Diagnosis and Treatment

If you have cat eye syndrome, that means you were born with it. Typically, your healthcare provider will diagnose you or your child based on the symptoms you 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's 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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  1. Genetic and Rare Diseases Information Center. Cat Eye Syndrome. National Center for Advancing Translational Sciences. U.S. Department of Health and Human Services. National Institutes of Health. Updated April 13, 2015.

  2. National Organization for Rare Disorders (NORD). Cat Eye Syndrome. Published 2017.