Introduction

Cat eye syndrome (CES) is a rare genetic condition that affects multiple parts of the body. A person affected by CES has an extra tiny piece of chromosome 22. This extra piece is a tiny extra mini-chromosome, and because of it, some parts of chromosome 22 appear foursome instead of 2. This is called a partial tetrasomy. Such extra genetic material can cause changes in how the body develops and result in it having certain physical features. This article will guide you through the physical features of this condition.¹

Visible physical features

The most common visible physical features of CES include:^2,3

• Cat-like eyes: Iris coloboma is a keyhole-shaped defect in the iris of the eye that gives the pupil a cat-like look. About half of the people with CES have this distinctive eye feature. Severe colobomas can affect vision and even cause blindness, but some individuals have only mild eye complications
• Ear skin tags or pits: These are small skin growths (tags) or dimples (pits) located just in front of the ears. These are benign (not harmful) but quite noticeable
• Face and head shape differences: Craniofacial abnormalities can include a wide set of eyes (hypertelorism), eyelids that slant slightly downward (down-slanting palpebral fissures), a flat nose bridge (broad nasal bridge) or a small lower jaw (micrognathia). Some babies may also be born with a split roof of the mouth (cleft palate). These features occur because the face and head didn’t develop in the usual way during early growth in the womb
• Short height and bone differences: Many children with CES are shorter than other children their age (short stature). Some may have a curved spine (scoliosis) or have the bones in the spine stuck together (vertebral fusion). Some might have missing ribs or extra ones. These differences are caused by changes in how the bones grow before birth (mesenchymal tissue maldevelopment). Doctors usually keep an eye on growth and may refer the person affected by CES to an orthopaedic specialist if needed
• Hearing loss: Some children may have mild hearing loss. These changes happen because the parts of the body that form the ears did not develop the usual way (branchial arch dysgenesis)

Internal organ differences

The most common internal organ differences in CES include:²

• Heart defects: approximately half of individuals with CES are born with a congenital heart defect. These can range from holes in the heart wall to more complex issues. Some of the more serious conditions may include atrioventricular septal defects or abnormalities in the structure of the major arteries
• Kidney abnormalities: CES can cause a range of kidney problems. Some newborns have only one kidney (called unilateral renal agenesis), while some have kidneys that did not form right (dysplatic kidneys). Having dysplastic kidneys could mean that they may not work as well as they should. In some cases, one kidney may have two drainage systems inside it (duplex collecting system). These kidney problems can lead to things like urine infections or issues with how the body gets rid of the waste. Doctors normally check the kidneys via scans after diagnosis to make sure they are performing their normal functions
• Genital abnormalities: because the kidneys and the genitalia grow from the same tissue in the womb, some people with CES also have changes in those areas. Boys might have testicles that have not dropped into the scrotum (undescended testicles/cryptorchidism). Girls might have a uterus or vagina that did not form completely (underdeveloped uterus or vaginal agenesis). These changes normally become noticeable around puberty

Digestive and elimination issues

Anal atresia is a malformation where the anal opening is missing or blocked at birth. This is a serious but correctable defect. Babies born with anal atresia require surgery to correct the malformation. Some newborns may have a milder form called anal stenosis, which is a narrow anal opening instead of complete atresia.^2,3

Why do symptoms vary so much in CES?

People with CES can experience very different symptoms and levels of severity. Even two family members with CES might be affected in completely different ways. Some people will only show mild features (or even no obvious symptoms) while others will show multiple serious health issues. Doctors are not entirely sure why the effects of CES vary so widely from person to person. One reason may be that not all of a person’s cells carry the extra chromosome material. This is called mosaicism, where some cells have the genetic change and some do not. Mosaicism can result in milder symptoms because fewer cells are affected. 

Another possible factor is that there may be additional genetic differences or modifiers that scientists have not identified yet, which could influence how severe the syndrome is. Considering these complexities, it is impossible to predict exactly which symptoms (if any) a child with CES will have, even if the chromosomal abnormality is the same. The outcome can range from very mild to quite serious, and each person’s case is unique.

Summary

Cat Eye Syndrome (CES) is a rare genetic condition caused by an extra piece of chromosome 22. This can lead to a bunch of different physical traits. Some common ones are cat-like eyes, skin tags near the ears and facial differences. It can also cause hearing loss and a cleft palate. Many people with CES have heart defects, kidney problems and genital differences. A blocked or missing anal opening is another possible feature of the condition. Children might be shorter than average, have spine or rib issues and have delays in their development. How bad the symptoms are varies a lot. Some people have only mild signs, while others have more serious problems. This is partly because not all cells have the extra chromosome. Because of all this, each case of CES is different. Doctors confirm the diagnosis with genetic tests and then do check-ups that follow a care guide. There is no cure, but many symptoms can be treated or managed with support from doctors, therapists and educators. With early care and regular check-ups, many people with CES can live healthy and full lives.

FAQs

Can CES be inherited? 

Most of the time, CES is not inherited. It usually happens by chance when a baby is forming in the womb. However, in very rare cases, a parent can pass it down if they carry the extra piece of chromosome 22 themselves. If passed down, it follows a pattern called autosomal dominant inheritance, meaning only one copy of the extra piece (from one parent) is enough to cause the condition.^4,5

How Is CES diagnosed?

• Prenatal Diagnosis:

CES can sometimes be spotted before birth during a routine pregnancy scan. If doctors see unusual features, like problems with the heart or kidneys, they may suggest a genetic test called amniocentesis. This test checks the baby’s chromosomes for extra genetic material from chromosome 22. If CES is confirmed, it helps doctors and families prepare for any care the baby might need after birth.³

• Postnatal Diagnosis:

If not found during pregnancy, CES can be diagnosed after birth based on physical signs like iris coloboma or anal atresia (see above). Doctors will confirm it using genetic tests such as a karyotype, fluorescent in-situ hybridisation (FISH), or chromosomal microarray, which can detect the extra piece of chromosome 22. Once diagnosed, the child usually has further check-ups to look for heart, kidney, or other issues so that care can begin early.³

Is there a cure for CES?

There is currently no cure for Cat Eye Syndrome, but there are many treatments to manage the symptoms and health problems. Care for a person with CES is personalised and often involves a team of specialists, which may include paediatricians, heart doctors, eye doctors, surgeons and others. It all depends on the person’s needs. 

How is CES treated?

Treatment focuses on addressing each specific issue. For example, if a child has a heart defect, a surgery can correct it. If they have growth delays or short stature, growth hormone therapy might be considered. If there are learning or developmental challenges, early intervention and special education can help. Supportive therapies such as physical or occupational therapy are also used as needed. With appropriate medical care and support, many individuals with CES can grow and thrive, and most have a normal or near-normal life expectancy.³