Supernumerary ring chromosome 20 characterized by fluorescence in situ hybridization

Clin Genet. 1996 Jan;49(1):49-53. doi: 10.1111/j.1399-0004.1996.tb04325.x.


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.

Publication types

  • Case Reports

MeSH terms

  • Abnormalities, Multiple / genetics*
  • Adult
  • Chromosomes, Human, Pair 20*
  • Developmental Disabilities / genetics
  • Follow-Up Studies
  • Humans
  • In Situ Hybridization, Fluorescence
  • Infant
  • Male
  • Mosaicism*
  • Phenotype
  • Ring Chromosomes*