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Mosaic trisomy 13: understanding origin using SNP array
  1. Natini Jinawath1,2,
  2. Regina Zambrano1,3,
  3. Elizabeth Wohler4,
  4. Maria K Palmquist1,5,
  5. Julie Hoover-Fong1,6,
  6. Ada Hamosh1,6,
  7. Denise A S Batista1,4,7
  1. 1Institute of Genetic Medicine, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA
  2. 2Research Center, Faculty of Medicine, Ramathibodi Hospital, Mahidol University, Bangkok, Thailand
  3. 3Department of Pediatrics, Louisiana State University Health Science Center and Children's Hospital, New Orleans, Louisiana, USA
  4. 4Kennedy Krieger Institute, Cytogenetics Laboratory, Baltimore, Maryland, USA
  5. 5Sanford School of Medicine, University of South Dakota, Sioux Falls, South Dakota, USA
  6. 6Department of Pediatrics, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA
  7. 7Department of Pathology, Johns Hopkins Medical Institutions, Baltimore, Maryland, USA
  1. Correspondence to Dr Denise Batista, Department of Pathology, Johns Hopkins Medical Institutions, 600 N Wolfe Street, Park SB202, Baltimore, MD 21287, USA; dbatist1{at}


Background Trisomy 13 occurs in 1/10 000–20 000 live births, and mosaicism accounts for 5% of these cases. Phenotype and outcome of mosaic trisomy 13 are variable and poorly understood. Microsatellite analyses of trisomy 13 have indicated the high incidence of maternal meiotic origin and reduced recombination, but no study has focused on mosaic trisomy 13 in live born patients.

Methods and results Single-nucleotide polymorphism (SNP) array, fluorescence in situ hybridisation and bioinformatics analyses were performed in three cases of mosaic trisomy 13. Two cases of complete mosaic trisomy 13 originated from meiosis I non-disjunction followed by trisomic rescue; one had crossovers resulting in segmental uniparental disomy in the disomic line, and one had no crossover. Mosaicism for partial trisomy 13 in the third complex case either arose from meiosis II non-disjunction without crossover or in early mitosis followed by anaphase lags. The extra chromosome 13 was maternal in origin in all three cases. Mosaicism percentage calculated from B allele frequencies ranged from 30 to 50.

Conclusions Genotypes and copy number information provided by SNP array allow determination of parental origin and uniparental disomy status and direct quantification of mosaicism. Such information may lead to a better understanding of mechanisms underlying mosaic aneuploidies and the observed phenotypic variability and better prediction of recurrent risk.

  • Trisomy 13
  • mosaicism
  • SNP array
  • uniparental disomy
  • non-disjunction
  • diagnostics tests
  • getting research into practice
  • genetics
  • cytogenetics
  • molecular genetics

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  • Competing interests None.

  • Provenance and peer review Not commissioned; externally peer reviewed.

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