Two new cases of analphoid marker chromosomes
Article first published online: 18 SEP 2002
Copyright © 2002 Wiley-Liss, Inc.
American Journal of Medical Genetics Part A
Volume 116A, Issue 3, pages 284–289, 30 January 2003
How to Cite
Spiegel, M., Hickmann, G., Senger, G., Kozlowski, P. and Bartsch, O. (2003), Two new cases of analphoid marker chromosomes. Am. J. Med. Genet., 116A: 284–289. doi: 10.1002/ajmg.a.10916
- Issue published online: 26 DEC 2002
- Article first published online: 18 SEP 2002
- Manuscript Accepted: 19 JUL 2002
- Manuscript Received: 3 JUL 2001
- supernumerary marker chromosome;
- analphoid marker chromosome;
- trisomy 1q43q44;
- tetrasomy 15q24qter
Supernumerary marker chromosomes (SMCs) without detectable alphoid DNA represent a rare and interesting class of rearranged marker chromosomes. These SMCs are predicted to have a neocentromere and have been referred to as neocentric marker chromosomes (NMCs). We report the molecular cytogenetic characterization of two new cases of neocentromere-containing chromosomes, one on 1q43∼44 and one on 15q26. Both cases were examined using fluorescence in situ hybridization (FISH) with various alpha-satellite DNA probes, and no alphoid DNA was detected. In case 1, the NMC originated from the distal long arm of chromosome 1 by chromosomal microdissection and reverse painting. This marker lacked detectable chromosome 1q subtelomeric sequences, and therefore appeared to be a small ring chromosome. After genetic counseling with a high risk for a MCA/MR syndrome (trisomy 1q43 q44), the family continued the pregnancy. At age 6 months, the infant demonstrated no congenital or developmental anomalies. This is the first published example of a NMC derived from chromosome 1q. The marker may be one of the smallest, if not the smallest, human NMC reported to date. In case 2, fetal ultrasonography indicated a complex heart defect (abnormal return of lower vena cava, atrial septum malformation) and bilateral hydronephrosis. Molecular cytogenetic analysis showed an inverted duplication of the distal long arm of chromosome 15 (tetrasomy 15q24 qter). The pregnancy was terminated. Autopsy demonstrated polycystic left kidney and dysplastic right kidney. Case 2 represents the ninth report of a neocentromere on distal chromosome 15q, suggesting that this region may possibly especially support the formation of neocentromeres. © 2002 Wiley-Liss, Inc.