Cat eye syndrome (CES), also known as Schmid-Fraccaro syndrome, is a rare genetic condition present at birth. It stems from a chromosomal abnormality that affects various bodily systems and organs. The syndrome’s manifestations can differ significantly among individuals, ranging from very mild to severe.
Understanding the Syndrome
Cat eye syndrome is a chromosomal disorder characterized by the presence of extra genetic material from chromosome 22. Humans normally have two copies of each chromosome, including chromosome 22, which has a short arm (22p) and a long arm (22q). In individuals with CES, the short arm and a small portion of the long arm of chromosome 22 are duplicated. This results in three (partial trisomy) or four (partial tetrasomy) copies of this specific genetic region instead of the usual two.
The extra genetic material typically forms a small, extra chromosome known as a small supernumerary marker chromosome (sSMC). This sSMC usually contains two mirror copies of a segment of chromosome 22, specifically the 22pter-q11 region. The presence of this additional genetic information disrupts normal development, leading to the diverse range of symptoms observed in CES. Most cases of Cat eye syndrome occur randomly, without a family history of the condition, suggesting spontaneous errors during cell division.
Recognizing Physical Characteristics
Physical characteristics vary widely among individuals with Cat eye syndrome. One of the most distinctive features, present in about half of affected individuals, is coloboma of the iris, a gap or hole in the colored part of the eye that can make the pupil appear elongated, resembling a cat’s eye. Coloboma can also extend to other parts of the eye, such as the choroid and retina, potentially affecting vision.
Other commonly observed features include:
- Preauricular tags or pits, which are small skin growths or depressions located in front of the ears.
- Anal anomalies, such as imperforate anus, where the anal opening is absent or improperly formed, sometimes with an abnormal connection to another body cavity.
- Congenital heart defects, such as total anomalous pulmonary venous return.
- Kidney abnormalities, ranging from underdeveloped or missing kidneys to the presence of an extra kidney.
- Skeletal issues, like scoliosis, fused vertebrae, or missing ribs.
- Less common manifestations include cleft lip or palate, short stature, and intellectual disability, which is usually mild but can vary.
Diagnosis and Medical Management
Diagnosis
Diagnosis of Cat eye syndrome is typically initiated by observing characteristic physical features and is confirmed through genetic testing. Prenatal diagnosis is possible if certain characteristics are noted during an ultrasound, which may lead to further tests like amniocentesis. Postnatally, genetic testing methods, such as karyotyping, are used to analyze the number and structure of chromosomes to identify the extra chromosome 22 material. Fluorescence In Situ Hybridization (FISH) detects specific DNA sequences to pinpoint the extra genetic material. Chromosomal microarray analysis offers more precise genetic details.
Medical Management
Medical management is multidisciplinary, tailored to individual symptoms. Surgical interventions may be necessary to correct structural anomalies such as heart defects, anal malformations, cleft lip or palate, or skeletal issues. Ophthalmological care addresses eye abnormalities, and regular monitoring for complications like glaucoma is common. Developmental therapies, including physical, occupational, and speech therapy, are often recommended to support motor skills and communication.
Outlook and Support
Prognosis varies based on symptom severity. While some individuals may have very mild manifestations and experience a normal life expectancy, others with more severe heart or kidney abnormalities may face greater challenges. Early intervention and ongoing, coordinated medical care are important for managing the condition and improving quality of life.
Although there is no cure for the underlying chromosomal defect, treatment focuses on addressing specific symptoms and supporting development. Support networks and resources for affected individuals and their families can offer valuable information, emotional support, and practical guidance for navigating the complexities of living with Cat eye syndrome.