Ring chromosome 21 and reproductive pattern: a familial case and review of the literature

Fertil Steril. 2008 Nov;90(5):2004.e1-5. doi: 10.1016/j.fertnstert.2008.01.087. Epub 2008 Apr 18.


Objective: To characterize a ring chromosome 21 found in an infertile woman and in her mother.

Design: Case report.

Setting: Molecular and cytogenetics unit in a university-affiliated hospital.

Patient(s): A 32-year-old infertile woman, presenting a normal female phenotype without clinical signs or major dysmorphisms.

Intervention(s): Molecular cytogenetic analyses and genetic counseling.

Main outcome measure(s): Structure of chromosome ring 21 (r21) was better defined by fluorescent in situ hybridization and array comparative genomic hybridization.

Result(s): Proband chromosomal analysis detected a mosaicism with three cell lines: one with a chromosome ring 21 (94%), one 45,XX, -21 (4%), and one with a dicentric ring (2%). This ring was inherited from her mother, whose karyotype was 46,XX, r(21)/45,XX, -21 [98%, 2%]. In both cases, the ring breakpoint was in band 21q22.3, with a deletion of about 3.4 Mb.

Conclusion(s): When a new case of r(21) is found, an accurate molecular definition of the deletion extent is mandatory and prenatal diagnosis should be suggested in case of pregnancy. Even if a strict genotype-phenotype correlation is not easy, mainly owing to a paucity of molecularly defined cases and to the mosaicism problems, prenatal investigations allow excluding chromosome 21 nondisjunction or rearrangements of r(21) that can have a dramatic effect on the fetus phenotype.

Publication types

  • Case Reports
  • Review

MeSH terms

  • Adult
  • Chromosome Deletion*
  • Chromosomes, Human, Pair 21*
  • Comparative Genomic Hybridization
  • Female
  • Genetic Counseling
  • Genotype
  • Humans
  • In Situ Hybridization, Fluorescence
  • Infertility, Female / genetics*
  • Karyotyping
  • Mosaicism
  • Pedigree
  • Phenotype
  • Ring Chromosomes*