Alternate Names: Schmid-Fraccaro syndrome
Overview: Cat Eye syndrome is a rare chromosomal disorder wherein the short arm and a small region of the long arm of chromosome 22 are present either three or four times (trisomy or terasomy) rather than twice in normal body cells.
Characteristic/Phenotype: As what the name suggest, the most distinctive trait of the person with the disease is the partial absence of ocular tissue (coloboma), often affecting both eyes (bilateral) which is surprisingly found only in some affected individuals. Other distinctive phenotypes include absence (atresia) of the anal canal, with an abnormal passage (fistula) from the end portion of the large intestine (rectum) into abnormal locations (e.g., the bladder, vagina, or perineum) and misshapen ears with abnormal outgrowths of skin and small depressions in front of the outer ears (preauricular tags and pits). These three traits occur only on 41 % of afflicted individuals.
Other inconstant features include:
- mild hypertelorism (widely spaced eyes) with downslanting palpebral fissures
- cardiac defects
- cleft palate
- urinary tract anomalies (missing, extra, or underdeveloped kidneys)
- skeletal anomalies Moderate intellectual deficit (present among 32% of patients
- Short stature
- Scoliosis/Skeletal problems
- Micrognathia (smaller jaw)
- Cleft palate
Frequency: The estimated prevalence in the general population is 1 in 74 000. Transmission is possible through both sexes, with a risk of transmission to the offspring of about 50%.
Diagnosis: Karyotyping shows a marker indicated by a small supernumerary chromosome at the proximal part of chromosome 22. The marker is bicentric and bisatellited and results from an inverted duplication, seen in 5/6 cases, which makes it the most reliable diagnostic criterion for this syndrome.
Antenatal diagnosis is possible through karyotyping and Fluorescence In Situ Hybridization (FISH) analysis of prenatal samples.
Causes: The abnormally duplicated chromosomal material from the long arm of chromosome 22 (band q11)is caused by the inverted duplication which occurs de novo forming a small, supernumerary chromosome (a marker chromosome).
Additional Information: The marker chromosome is often present in a mosaic state.
No correlations have been identified between the severity of the intellectual deficit and the presence of malformations, and the degree of the mosaicism or the size of the duplication. However, patients carrying small chromosome 22 markers containing no euchromatin display no associated phenotype.
Treatment/Recommendations/Therapies: Complications associated with the syndrome can be treated, and a great deal can be done to provide support and compensate for disabilities. Evaluation and follow-up of people with cat eye syndrome comprises thorough examination of all parts of the body that may be affected.
The heart is examined using ultrasound (echocardiography). A paediatric cardiologist will decide on how to proceed with treatment. Some heart defects require surgical intervention. Children with heart defects should be monitored regularly.
Ultrasound examination is also used to evaluate the kidneys. Paediatric medical follow-up should be continued through childhood so that renal impairment can be detected as early as possible.
Children with anal atresia require early surgical intervention. Treatment and follow-up should be carried out in close cooperation with a pediatric medical clinic.
Urinary tract abnormalities are evaluated by a paediatric urologist, who will decide on treatment and assess the need for surgery.
An ophthalmologist uses several different examination methods and tests to identify any eye abnormalities and corresponding vision problems. Visually impaired children learn to optimise remaining vision by using visual aids and some may also find it helpful to learn other communication techniques, such as Braille.
Clefting requires surgical repair. Parents of children who have problems sucking and eating require early contact with a dietician and a speech therapist to establish good feeding routines.
Surgery is used to open and widen blocked nasal passages.
In order to stimulate the child’s development and compensate for loss of function, the child and the family also require early contact with a team composed of professionals with special expertise in how disability affects everyday life, health and development.
Support and treatment cover medical, educational, psychological, social and technical areas and are intended both to help the child develop fully and to help compensate for any disabilities.
Psychological evaluation is important for assessing the child’s developmental level, especially before starting school. Children with intellectual disability require special education, adapted to meet their needs. Speech, language and communication training is an important part of their education. A child with communication problems can be helped by an occupational therapist, a speech pathologist and a special education teacher, all contributing to the process of evaluating and trying out augmentative and alternative communication.
Genetic counselling is advisable for reproductive decisions.
Support for Disorders of Chromosome 22
Turleau, C. (2005). Cat-eye syndrome. Retrieved March 12, 2013 from the URL: http://www.orpha.net/consor/cgi-bin/OC_Exp.php?lng=en&Expert=195
NORD, Rare Disease Information. (2010). CAT EYE SYNDROME. Retrieved March 12, 2013 from the URL: http://www.rarediseases.org/rare-disease-information/rare-diseases/byID/1085/viewAbstract
Anneren, G. and Blennow, E. (2012). Cat eye syndrome. Retrieved March 12, 2013 from the URL: http://www.socialstyrelsen.se/rarediseases/cateyesyndrome