BACKGROUND: @entity3 ( @entity3 ) is currently used as a frontline screening test to identify fetuses with common @entity2007 . Occasionally, incidental @entity3 results are conveyed to the clinician suggestive of fetuses with rare chromosome disease syndromes. We describe a @entity1 with trisomy 9 (T9) mosaicism where the prenatal history reported a positive @entity3 result for T9 that was unconfirmed by conventional prenatal diagnosis. METHODS: @entity3 was performed by low coverage whole genome plasma DNA sequencing. Karyotyping and fluorescent in situ hybridization (FISH) analysis with chromosome 9p-ter and 9q-ter probes was used to determine the somatic cell level of T9 mosaicism in the fetus and @entity1 . Quantitative fluorescent PCR (Q-PCR) of highly polymorphic short tandem repeat (STR) chromosome 9 markers was also performed to investigate the nature of the T9 mosaicism and the parental origin. RESULTS: A 22  month old @entity1 presented with severe @entity245 , @entity1779 and @entity299 consistent with phenotypes associated with T9 mosaicism syndrome. Review of the prenatal testing history revealed a positive @entity3 result for chromosome T9. However, follow up confirmatory karyotyping and FISH analysis of fetal cells returned a normal karyotype. Post-natal studies of somatic cell T9 mosaicism by FISH detected levels of approximately 20  % in blood and buccal cells. Q-PCR STR analysis of family DNA samples suggested that the T9 mosaicism originated by post-zygotic trisomic rescue of a paternal meiotic II chromosome 9 non-disjunction error resulting in the formation of two distinct somatic cell lines in the proband, one with paternal isodisomy 9 and one with T9. CONCLUSION: This study shows that @entity3 may also be a useful screening technology to increase prenatal detection rates of rare fetal chromosome disease syndromes.

Birth of a XXXX with trisomy 9 mosaicism syndrome associated with paternal isodisomy 9: case of a positive noninvasive prenatal test result unconfirmed by invasive prenatal diagnosis.

@entity1 :: ('9606', 'Species') :: ['girl', 'child'] @entity2007 :: ('MESH:D000782', 'Disease') :: ['aneuploidies'] @entity245 :: ('MESH:D002658', 'Disease') :: ['developmental delay'] @entity3 :: ('MESH:D009362', 'Disease') :: ['Non-invasive prenatal testing', 'NIPT'] @entity299 :: ('MESH:D006331', 'Disease') :: ['congenital heart disease'] @entity1779 :: ('MESH:D002543', 'Disease') :: ['congenital cerebral dysplasia']
@entity1 :: (9606,Species) :: ['child']
