Cat eye syndrome (CES), also known as Schmid-Fraccaro syndrome, is a very rare genetic disorder that’s usually evident at birth.
It gets its name from the distinctive eye pattern present in about half of affected individuals. People with CES may have a defect called coloboma that results in an elongated pupil, which resembles a cat’s eye.
CES causes many other symptoms that vary in severity, including:
- heart defects
- skin tags
- anal atresia
- kidney problems
Some people with CES will have a very mild case and experience little to no symptoms. Others may have a severe case and experience a range of symptoms.
The symptoms of CES are highly variable. People with CES may have problems with the:
- reproductive organs
- intestinal tract
Some people may develop only a few features and symptoms. For others, the symptoms are so mild that the syndrome may never actually be diagnosed.
The most common features of CES include:
- Ocular coloboma. This occurs when a fissure in the lower part of the eye fails to close during early development, resulting in a cleft or gap. Severe coloboma may result in vision defects or blindness.
- Preauricular skin tags or pits. This is an ear defect that causes small growths of skin (tags) or slight depressions (pits) in front of the ears.
- Anal atresia. This is when the anal canal is absent. Surgery must correct it.
About two-fifths of people with CES have these three symptoms, referred to as the “classic triad of symptoms.” However, every case of CES is unique.
Other symptoms of CES include:
- other eye abnormalities, such as strabismus (crossing of the eyes) or having one abnormally small eye (unilateral microphthalmia)
- small or narrow anal opening (anal stenosis)
- mild hearing impairment
- congenital heart defects
- kidney defects, such as underdevelopment of one or both kidneys, absence of a kidney, or the presence of an extra kidney
- reproductive tract defects, such as underdevelopment of the uterus (females), absence of the vagina (females), or undescended testes (males)
- intellectual disabilities, which are usually mild
- skeletal defects, such as scoliosis (curvature of the spine), abnormal fusion of certain bones in the spinal column (vertebral fusions), or absence of certain toes
- biliary atresia (when the bile ducts fail to develop or develop abnormally)
- cleft palate (incomplete closure of the roof of the mouth)
- short stature
- abnormal facial features, such as downwardly slanting eyelid folds, widely spaced eyes, and a small lower jaw
CES is a genetic disorder that occurs when there’s a problem with a person’s chromosomes.
Chromosomes are structures that carry our genetic information. They can be found in the nucleus of our cells. Humans have 23 paired chromosomes. Each one has:
- a short arm labeled as “p”
- a long arm labeled by the letter “q”
- a region where the two arms connect, called the centromere
Normally, people have two copies of chromosome 22, each with a short arm called 22p and a long arm called 22q. People with CES have two extra copies of the short arm and a small region of the long arm of chromosome 22 (22pter-22q11). This causes abnormal development during the embryo and fetal stages.
The precise cause of CES isn’t known. The extra chromosomes are usually not inherited from a parent, but rather appear to arise randomly when an error occurs when the reproductive cells divide.
In these cases, the parents have normal chromosomes. CES occurs in just 1 out of every 50,000 to 150,000 live births, estimates the National Organization for Rare Disorders.
However, there are a few inherited cases of CES. If you have the condition, there’s a high risk you’ll pass the extra chromosome to your children.
A doctor may first notice a birth defect that could suggest CES before a baby is born with an ultrasound test. An ultrasound uses sound waves to produce an image of the fetus. It may reveal certain defects characteristic of CES.
If your doctor observes these features on an ultrasound, they may order follow-up testing, such as amniocentesis. During amniocentesis, your doctor takes a sample of the amniotic fluid to analyze it.
Doctors can diagnose CES by the presence of extra chromosomal material from chromosome 22q11. Genetic testing can be done to confirm the diagnosis. This testing may include:
- Karyotyping. This test produces an image of a person’s chromosomes.
- Fluorescence in situ hybridization (FISH). It can detect and locate a specific DNA sequence on a chromosome.
Once CES is confirmed, your doctor will likely run additional tests to detect any other abnormalities that may be present, like heart or kidney defects.
These tests may include:
- X-rays and other imaging tests
- electrocardiography (EKG)
- eye examination
- hearing tests
- cognitive function tests
A treatment plan for CES depends on the individual’s symptoms. Treatment may involve a team of:
- heart specialists (cardiologists)
- gastrointestinal specialists
- eye specialists
There’s no cure for CES yet, so treatment is directed toward each specific symptom. This may include:
- surgery to correct anal atresia, skeletal abnormalities, genital defects, hernias, and other physical issues
- physical therapy
- occupational therapy
- growth hormone therapy for people with very short stature
- special education for those with intellectual disabilities
The life expectancy for people with CES varies widely. It depends on the severity of the condition, especially if there are heart or kidney problems. Treatment for individual symptoms in these cases can prolong life.
Some people with CES will have severe malformations in early infancy, which can lead to a much shorter life expectancy. However, for most people CES, life expectancy usually isn’t reduced.
If you have CES and plan to get pregnant, you may want to talk to a genetic counselor about the risk of passing the condition on.