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Use of tissue samples in diagnosing diploid triploid mosaicism
  1. Oisín Mahon1,
  2. Áine Fox2,
  3. Sally Ann Lynch3 and
  4. Katie Cunningham2
  1. 1Royal College of Surgeons in Ireland, Dublin, Ireland
  2. 2Neonatology, Rotunda Hospital Neonatal Unit, Dublin, Ireland
  3. 3Genetics, Our Lady's Children's Hospital, Crumlin, Ireland
  1. Correspondence to Dr Oisín Mahon; oisinmahon{at}


Diploid triploid mosaicism (DTM) is a rare genetic condition where there is an extra haploid set of chromosomes in mosaic form. We describe an infant for whom DTM was detected antenatally through amniocentesis. Prenatal counselling suggested a guarded prognosis. The infant’s phenotypic presentation and postnatal course reflect the varied presentation and prognosis associated with DTM. We highlight potential challenges in diagnosing DTM postnatally, with many having normal blood karyotype with 46 chromosomes.

  • Neonatal health
  • Congenital disorders
  • Developmental Paediatrics
  • Genetic screening / counselling
  • Materno-fetal medicine

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  • Contributors OM and ÁF collected relevant patient data, reviewed the available literature, wrote the body of the report and performed the final editing. SAL provided expertise on the topic, as well as contributed to the drafting and editing of the report. KC was the lead clinician on the case and was involved in drafting and editing the report. All authors approved the content of the submitted report.

  • Funding The authors have not declared a specific grant for this research from any funding agency in the public, commercial or not-for-profit sectors.

  • Case reports provide a valuable learning resource for the scientific community and can indicate areas of interest for future research. They should not be used in isolation to guide treatment choices or public health policy.

  • Competing interests None declared.

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