Cat Eye Syndrome

Description

Cat Eye Syndrome (CES) is a rare genetic disorder characterized by a distinctive eye abnormality that resembles a cat‘s eye. It can also affect other body systems, leading to a range of physical features and health concerns. This blog post will provide comprehensive information about CES, including its causes, symptoms, diagnosis, management, and ways to thrive with this condition.

Genes Involved

Genes Involved in Cat Eye Syndrome:

Chromosomal Abnormality: Cat Eye Syndrome is caused by a chromosomal abnormality known as a supernumerary marker chromosome (SMC), which is an extra piece of chromosome material.
Specific SMC: The specific SMC responsible for CES is called the "22q11.2 supernumerary marker chromosome." This marker chromosome contains genetic material from chromosome 22, specifically the region 22q11.2.
Variability in Size and Content: The size and content of the SMC can vary, which explains the wide range of symptoms seen in people with CES.

Recognizing the Signs and Symptoms

Recognizing the Signs and Symptoms of Cat Eye Syndrome:

Distinctive Eye Abnormalities: The most prominent feature of CES is the presence of a coloboma (a gap or cleft) in the iris, giving the appearance of a cat‘s eye. This coloboma can be unilateral (affecting one eye) or bilateral (affecting both eyes).
Other Eye Problems: CES can also cause other eye problems, such as microphthalmia (small eyes), anophthalmia (absence of eyes), strabismus (crossed eyes), and cataracts.
Hearing Loss: Some individuals with CES experience hearing loss, often due to abnormalities in the ear.
Heart Defects: Heart defects, such as ventricular septal defects and patent ductus arteriosus, are common in people with CES.
Genitourinary Abnormalities: Abnormalities in the urinary and reproductive systems can occur, including hypospadias (an opening of the urethra on the underside of the penis), cryptorchidism (undescended testes), and renal agenesis (absence of a kidney).
Skeletal Abnormalities: Skeletal problems, such as scoliosis (curvature of the spine), clubfoot, and polydactyly (extra fingers or toes), may be present.
Intellectual Disability: Some individuals with CES may have intellectual disabilities, but the severity can vary.
Other Features: Other features of CES may include cleft palate, gastrointestinal malformations, and skin abnormalities.

Causes

Causes of Cat Eye Syndrome:

Chromosomal Abnormality: CES is caused by a chromosomal abnormality, specifically the presence of a supernumerary marker chromosome (SMC) containing genetic material from chromosome 22.
Random Occurrence: The SMC is usually a random event that occurs during the formation of egg or sperm cells.
Not Inherited: In most cases, CES is not inherited from parents. However, there is a small chance of recurrence if a parent carries a balanced translocation, which could lead to the formation of the SMC in their offspring.

Inheritance/recurrence risk

Inheritance and Recurrence Risk in Cat Eye Syndrome:

Sporadic: Cat Eye Syndrome is typically a sporadic event, meaning it occurs randomly in individuals without a family history.
Balanced Translocation: While CES is usually not inherited, if a parent carries a balanced translocation involving chromosome 22, there is a small risk of transmitting the SMC to their offspring.
Recurrence Risk: The recurrence risk for CES is generally low but depends on the specific chromosomal abnormality and whether a parent carries a translocation.
Genetic Counseling: Genetic counseling can help families understand the risks of recurrence and make informed decisions about future pregnancies.

WES Whole Exome Sequencing