Transmission of ring chromosome 13 from a mother to daughter with both having a 46,XX, r(13)(p 13q34) karyotype

Jirair K. Bedoyan, Leigh Anne Flore, Aziz Alkatib, Salah A. Ebrahim, Erawati V. Bawle

Research output: Contribution to journalArticlepeer-review

17 Scopus citations


Ring chromosomes are thought to be the result of breakage in both arms of a chromosome, with fusion of the points of fracture and loss of the distal fragments. Another mechanism of ring formation is believed to be the simple fusion of chromosome ends with preservation of telomeric and subtelomeric sequences. Ring chromosome 13 was first described in 1968 and its incidence estimated at 1 in 58,000 live births. Severe phenotypes associated with large deletions of 13q have been described as "ring chromosome 13 syndrome." Features of the "ring chromosome 13 syndrome" include mental retardation (often severe), growth retardation, microcephaly, facial dysmorphism, and hand, foot or toe abnormalities. We report on a case of a mother and daughter with r(13) and mild phenotypes. Our patient, IA, had chromosome analysis performed at about 41/2 years of age due to some developmental delay. This revealed 46,XX, r(13)(p13q34) karyotype with no loss of any chromosomal band. Her mother, EA, was subsequently found to have the same ring 13. IA's maternal grandmother had a normal karyotype while her maternal grandfather was unavailable for testing. Fluorescence in situ hybridization (FISH) analysis showed loss of a specific subtelomeric 13q region in r(13) in the mother. Clinically, IA had macular hyperpigmentation on the chin and mild delay in speech and fine motor skills. EA, 22 years of age, had mild short stature and borderline mental retardation. To our knowledge, this is the first report of a case of familial transmission of r(13). We compare phenotypes of our cases with those from other reported cases of r(13) and discuss the possible mechanism of formation of this ring chromosome.

Original languageEnglish
Pages (from-to)316-320
Number of pages5
JournalAmerican Journal of Medical Genetics, Part A
Volume129 A
Issue number3
StatePublished - Sep 1 2004


  • FISH, telomeres
  • Familial
  • Malformations
  • Mental retardation
  • Ring chromosome


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