FISH of supernumerary marker chromosomes (SMCs) identifies six diagnostically relevant intervals on chromosome 22q and a novel type of bisatellited SMC(22)

Supernumerary marker chromosomes (SMCs) are frequently found at pre- and postnatal cytogenetic diagnosis and require identification. A disproportionally large subset of SMCs is derived from the human chromosome 22 and confers tri- or tetrasomy for the cat eye chromosomal region (CECR, the proximal 2 Mb of chromosome 22q) and/or other segments of 22q. Using fluorescence in situ hybridization (FISH) and 15 different DNA probes, we studied nine unrelated patients with an SMC(22) that contained the CECR. Five patients showed the small (type I) cat eye syndrome (CES) chromosome and each one had the larger (type II) CES chromosome, small ring chromosome 22, der(22)t(11;22) extrachromosome, and a …