Send to

Choose Destination
Genet Med. 2013 Jan;15(1):3-13. doi: 10.1038/gim.2012.78. Epub 2012 Aug 30.

A systematic analysis of small supernumerary marker chromosomes using array CGH exposes unexpected complexity.

Author information

Medical Genetics and Genomics Laboratory, Kaiser Permanente Southern California, Los Angeles, California, USA.



A small supernumerary marker chromosome is often seen in patients with developmental disorders. Prior to array-based comparative genomic hybridization markers were rarely genotyped end to end. In this study, a valid genotype-to-phenotype correlation was possible because the supernumerary marker chromosomes were fully characterized by array-based comparative genomic hybridization in a genome-wide analysis.


Ten consecutive de novo small supernumerary marker chromosome cases were systematically genotyped using G-banding, C-banding, AgNOR staining, whole-genome array-based comparative genomic hybridization, and fluorescence in situ hybridization.


Among 10 small supernumerary marker chromosome cases studied, 4 (40%) were not identified by array-based comparative genomic hybridization because of low-level mosaicism or because they lacked euchromatin. One case (10%) was a simple pericentromeric marker extending from 5p13.3 to 5q11.2. Five (50%) markers showed unexpected complexity. Two cases had markers that were derivative acrocentric (AgNOR+) chromosomes with the euchromatin from chromosomes 18p or 19p. Each of the other three cases with complex markers had unusual characteristics including a marker from noncontiguous segments of chromosome 19q, a highly complex rearrangement involving a chromosome 20 homolog as well as the small supernumerary marker chromosome, and a mosaic duplication of a proximal 8p marker.


Small supernumerary marker chromosomes are frequently complex on the basis of our small sample. Whole-genome array-based comparative genomic hybridization characterization of the small supernumerary marker chromosome provided informed genetic counseling.

[Indexed for MEDLINE]

Supplemental Content

Full text links

Icon for Nature Publishing Group
Loading ...
Support Center