title: [Cytogenetic analysis and phenotype location analysis on the karyotype of a ring chromosome 21 syndrome].
abstract: OBJECTIVE
  To search the forming cause and the correlation between the clinical phenotype and chromosome band by the cytogenetic analysis on a case of ring chromosome 21 syndrome.
  
  
  METHODS
  Identification and location of 21 ring chromosome were performed with the G-banding, C-banding, N-banding, high-resolution banding and fluorescence in situ hybridization (FISH) techniques.
  
  
  RESULTS
  It was found that the karyotypes of the patient's parents are normal. The patient's karyotype is 46,XY, r(21)[91]/46,XY,r(21;21)(p11q22.3;p11q22.3) [5]/45,XY,-21[4].
  
  
  CONCLUSIONS
  The clinical phenotype of ring chromosome 21 syndrome is related to the deletion of distal segment of 21q, and the abnormal sexual development of male is related with the deletion of 21q22.3.
authors.affiliation: Pediatric Research Institute of Children's Hospital, Changsha, Hunan, P. R. China. zxycgh@163.com
authors.forename: Xing-yuan
authors.initials: XY
authors.lastname: Zhu
authors.forename: Rui
authors.initials: R
authors.lastname: Zhao
authors.forename: Zhi-chun
authors.initials: ZC
authors.lastname: Ye
authors.forename: You-gong
authors.initials: YG
authors.lastname: Peng
authors.forename: Yue-qiu
authors.initials: YQ
authors.lastname: Tan
mesh_terms: D002675:Child, Preschool; D002869:Chromosome Aberrations; D025063:Chromosome Disorders / Q000235:genetics / Q000473:pathology; D002891:Chromosomes, Human, Pair 21 / Q000235:genetics*; D020732:Cytogenetic Analysis / Q000379:methods*; D006801:Humans; D017404:In Situ Hybridization, Fluorescence; D007621:Karyotyping; D008297:Male; D010641:Phenotype; D012303:Ring Chromosomes; D013577:Syndrome