Further delineation of the supernumerary chromosome in the Cat-Eye syndrome.

A clinical diagnosis of the Cat-Eye Syndrome (CES) was made in a female child with anal stenosis, congenital heart disease, bilateral preauricular skin tags and coloboma of the right fundus. The karyotype was 46XX/47XX, +mar. Q-banding revealed the marker chromosome to be metacentric and comparable in size to that of a G-group chromosome. One arm had brightly fluorescent satellites while the other exhibited a fluorescent polymorphism similar to the short arm of a D- or G-group chromosome. Chromosome analysis from blood cultures obtained from parents and three sibs did not demonstrate the presence of the marker chromosome. Comparison of the fluorescent polymorphisms revealed that the satellites on the marker were comparable in size and brightness to those of the maternal chromosome 22. C-banding demonstrated the marker to be dicentric. While there has been much speculation on the origin of the Cat-Eye Chromosome (CEC) based on clinical features in common with the trisomy 22 syndrome, autoradiographic studies and the general appearance of the marker, this case provides definitive evidence for the involvement of chromosome 22 in the origin of the marker chromosome. This chromosome is interpreted as the product of a Robertsonian translocation between the short arm and satellites of chromosome 22 and the short arm of another D- or G-group chromosome, most likely 13. Thus, the karyotype of the patient is 46XX/47XX, t(?13;22) (?13pter13q11::22q1122pter). Reinvestigation of patients with CES utilizing heritable polymorphisms may better elucidate the specific nature of the marker, and further delineate a possible basis for the heterogeneity of the disorder.