Supernumerary marker chromosomes detected in 100,000 prenatal diagnoses: molecular cytogenetic studies and clinical significance.
OBJECTIVE
To evaluate the clinical significance of the supernumerary marker chromosomes (SMCs) detected during prenatal diagnosis.


METHODS
We retrospectively studied cytogenetic/fluorescence in situ hybridization (FISH) results and clinical evaluation of 110 marker cases identified from approximately 100,000 cases referred for prenatal diagnosis. The clinical follow-up performed was focused on cases with de novo markers not derived from chromosome 15.


RESULTS
Among the 110 SMCs, 79 (71.8%) were de novo, 24 (21.8%) were familial, and the origin was undetermined in 7 cases. Fifty-eight of the SMCs originated from nonacrocentric chromosomes and 52 SMCs were derived from acrocentric chromosomes, with 27 originating from chromosome 15. Twenty-two of the SMCs from chromosome 15 did not contain the Prader-Willi/Angelman syndrome critical region, and uniparental disomy was ruled out in 19/19 cases. Clinical information ranging from birth to 4 years was obtained for 46 de novo cases with nonchromosome-15-derived SMCs. Of these cases, 11/11 acrocentric SMCs resulted in normal phenotype. In contrast, 4/23 cases with single nonacrocentric SMCs and 3/5 cases with two or more SMCs resulted in an abnormal phenotype.


CONCLUSIONS
Our data suggests an overall low risk for acrocentric SMCs and a higher risk for nonacrocentric SMCs. Phenotypes associated with markers derived from some specific chromosomes are also discussed.
Huang
Bing
B
Genzyme Genetics, Orange, CA 92868, USA. bihuang@genzyme.com
Solomon
Sharon
S
Thangavelu
Maya
M
Peters
Katherine
K
Bhatt
Sucheta
S
D025063:Chromosome Disorders / Q000175:diagnosis / Q000235:genetics*; D002877:Chromosomes, Human / Q000235:genetics*; D002884:Chromosomes, Human, Pair 15; D020732:Cytogenetic Analysis / Q000379:methods*; D005260:Female; D005819:Genetic Markers; D005820:Genetic Testing; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D011247:Pregnancy; D011296:Prenatal Diagnosis / Q000379:methods*; D012189:Retrospective Studies
D005819:Genetic Markers