Diagnosis criteria typically requires at least two of the ocular coloboma, anal atresia, and renal malformations; or one of the above accompanied by minor symptoms; or the combination of any five or more minor symptoms . Cat Eye Syndrome is estimated to afflict 1 in 50,000 to 1 in 150,000 .
Preauricular pits and tags, and mild retardation of development and growth– which have a frequency of occurrence of 87% and 50% respectively—are other serious symptoms that encourage a CES diagnosis .
These diagnoses are verified cytogenetically: usually in the form of FISH (fluorescence in-situ hybridization) analysis. FISH confirms the presence of a “Type I” or “Type II” Cat Eye Syndrome chromosomes . “Type I” is the more common cause of CES . Researchers have been unable to find a correlation between chromosome type and phenotype severity due to conflicting clinical findings.
Although FISH is often used by medical professionals there is currently no standard test used to diagnose CES. Cytogenetic blood testing is another popular method used. Both will confirm the presence of the supernumerary marker chromosome . In rare cases the marker chromosome will not be present. It is theorized that this occurs when the marker chromosome in present during embryonic development but disappears afterwards . Only a handful of CES patients have been noted to have this variation of CES.
Individuals who would like to obtain more information are encouraged to contact local health services to access cytogenetic services. Those in the Greater Vancouver area can obtain this service through Vancouver Coastal Health lab services.
Prenatal diagnosis of CES is also made possible by FISH. Further details, such as fetal phenotype, can be obtained via 3D ultrasounds: however, the phenotype may not be definitive as case studies have shown individuals to develop new symptoms over time. See picture of a 3D ultrasound. Amniocentesis is another prenatal diagnostic method through the search for the presence of the supernumerary marker chromosome.