Tertiary trisomy due to a reciprocal translocation of chromosomes 5 and 21 in a four-generation family

Stephen R. Braddock, Kimberly M. Henley, Karen L. Potter, Hieu G. Nguyen, Tim Hui Ming Huang

Research output: Contribution to journalArticle

6 Scopus citations

Abstract

Tertiary trisomy, or double trisomy, is a rare occurrence. We present two individuals with a previously unreported tertiary trisomy for chromosomes 5p and 21q in an eight-generation pedigree. Their phenotypes are compared with other partial trisomies of either 5p or 21q from the literature. The propositus was diagnosed with trisomy 21 at 2 years of age after a karyotype study for short stature and developmental delay. His phenotype was described as atypical for Down syndrome. He presented at 9 years of age because of pervasive behavioral problems and obesity. He was brachycephalic with a flattened nasal bridge, but he lacked other characteristics of trisomy 21. Because of lack of phenotypic evidence of Down syndrome, a repeat karyotype was obtained and showed 47,XY,+der(21)t(5;21)(p15.1; q22.1), incorporating- partial trisomies of both chromosomes 5 and 21. Mother had a balanced translocation, 46,XX,t(5;21)(p15.1; q22.1); 8 other relatives were examined. The translocation originated from the maternal great-grandmother, but only the propositus and his mentally retarded aunt had a similar phenotye and the derivative chromosome. Fluorescence in situ hybridization showed absence of band 21q22.2 in the derivative chromosome of the propositus and his aunt, indicating that neither had trisomy for the Down syndrome critical region. These cases represent a unique double partial trisomy of chromosome arms 5p and 21q that occurred because of 3:1 malsegregation of a reciprocal translocation. These cases further demonstrate that phenotypic discordance with cytogenetic results dictate further investigation using advanced cytogenetic hybridization. (C) 3000 Wiley-Liss, Inc.

Original languageEnglish (US)
Pages (from-to)311-317
Number of pages7
JournalAmerican Journal of Medical Genetics
Volume92
Issue number5
DOIs
StatePublished - Jun 19 2000
Externally publishedYes

Keywords

  • 3:1 malsegregation
  • Chromosome 21
  • Chromosome 5
  • Double trisomy
  • Tertiary trisomy
  • Translocation

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)

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