Mosaic down syndrome in a patient with low-level mosaicism detected by microarray

Eyby Leon, Ying S. Zou, Jeff M. Milunsky

Research output: Contribution to journalArticlepeer-review

16 Scopus citations


Down syndrome (DS) is the most common aneuploidy in liveborns with an estimated frequency of 1 in 650-1,000 births. Approximately 1-2% of all live-born DS individuals have mosaicism. The correlation between the percentage of mosaicism and the severity of the phenotype in mosaic trisomy 21 has been determined in previous studies. Patients with low percent of trisomy 21 have less phenotypic manifestations, higher IQs, and better overall survival. We report on a 1-day-old baby girl with subtle features of DS and low-level trisomy 21 mosaicism (8-13% in lymphocytes, 31% in buccal cells) with normal high resolution chromosome analysis. The aneuploidy was detected by 6.0 SNP microarray and confirmed by fluorescent in situ hybridization (FISH). Further studies to detect mosaicism are recommended from blood (using interphase FISH) or other tissues in the evaluation of a child with features of DS and a normal blood metaphase karyotype. SNP microarray technology appears to be a useful adjunct, being able to detect low-level mosaicism in these cases.

Original languageEnglish (US)
Pages (from-to)3154-3156
Number of pages3
JournalAmerican Journal of Medical Genetics, Part A
Volume152 A
Issue number12
StatePublished - Dec 1 2010
Externally publishedYes


  • Down syndrome
  • Microarray
  • Mosaicism
  • SNP
  • Trisomy 21

ASJC Scopus subject areas

  • Genetics
  • Genetics(clinical)


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