Supernumerary ring chromosome 20 characterized by fluorescence in situ hybridization.
We report on a boy with mild dysmorphic features and developmental delay, in whom karyotyping showed an additional minute ring chromosome in 60% of metaphases. Fluorescence in situ hybridization (FISH) with a centromere specific probe demonstrated that the ring chromosome contained the centromeric region of chromosome 20. The ring was highlighted completely using a chromosome 20 painting probe. A cosmid probe for 20p 12-13 gave a positive signal and hybridization with an all-telomere probe showed on signal, suggesting a breakpoint in the 20p telomere. The results suggested that only a small part of 20q was involved in this ring. The ring was also detected in 18% of nuclei of a buccal smear. The phenotypic similarities of symptoms in the proband to patients with a (partial) trisomy 20p and the dissimilarities to symptoms in patients with (partial) trisomy 20q were in agreement with the FISH results.
van Langen
I M
IM
Institute of Human Genetics, University of Amsterdam, The Netherlands.
Otter
M A
MA
Aronson
D C
DC
Overweg-Plandsoen
W C
WC
Hennekam
R C
RC
Leschot
N J
NJ
Hoovers
J M
JM
D000015:Abnormalities, Multiple / Q000235:genetics*; D000328:Adult; D002890:Chromosomes, Human, Pair 20; D002658:Developmental Disabilities / Q000235:genetics; D005500:Follow-Up Studies; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007223:Infant; D008297:Male; D009030:Mosaicism; D010641:Phenotype; D012303:Ring Chromosomes