De novo mosaic and partial monosomy of chromosome 21 in a case with superior vena cava duplication
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CASE REPORT
De novo mosaic and partial monosomy of chromosome 21 in a case with superior vena cava duplication Abul Kalam Azad1* , Lindsay Yanakakis2, Samantha Issleb2, Jessica Turina2, Kelli Drabik2, Christina Bonner3, Eve Simi2, Andrew Wagner2, Morry Fiddler2 and Rizwan Naeem1,2
Abstract Background: Full or partial monosomy of chromosome (chr) 21 is a very rare abnormal cytogenetic finding. It is characterized by variable sizes and deletion breakpoints on the long arm (q) of chr 21 that lead to a broad spectrum of phenotypes that include an increased risk of birth defects, developmental delay and intellectual deficit. Case presentation: We report a 37-year-old G1P0 woman initially screened by non-invasive prenatal testing with no positive findings that was followed by an 18-week anatomy scan with a fetal finding of duplication of the superior vena cava (SVC). The medical and family history was otherwise uneventful. After appropriate genetic counseling, amniocentesis was performed to evaluate suspected chromosomal anomalies. Conclusions: Interphase fluorescent in situ hybridization revealed loss of one chr 21 signal that was further delineated by chromosomal microarray analysis on uncultured amniocytes as a terminal 10 Mb deletion on chr 21q. Karyotype and microarrays on cultured amniocytes showed two cell lines for a mosaic 21q terminal deletion and monosomy 21. The combined molecular cytogenetics results reported following the ISCN 2016 guideline as mos 46,XX,del(21)(q22)dn[20]/45,XX,-21dn[10].nuc ish(D21S342/D21S341/D21S259x1)[100].arr[GRCh37] 21q11.2q22.12(15412676_36272993)x1~2,21q22.12q22.3(36431283_47612400)x1. Parental chromosomal analysis revealed normal karyotypes. Thus, this was a de novo mosaic full and partial monosomy of chr 21 in a case with SVC duplication. Despite the association of congenital heart disease with monsomy 21 we could not find any published literature or online databases for this cytogenetic abnormality. The patient terminated the pregnancy following the abnormal molecular cytogenetic results due to the possible challenges the baby would face if carried to term. Keywords: Chromosome 21, Partial monosomy, Mosaicism, Superior vena cava duplication Background Monosomy 21 is a very rare cytogenetic anomaly caused by loss of chromosome (chr) 21 or deletion of variable regions of the long arm (q) of chr 21. To date only a handful of cases have been described the anomaly/condition
*Correspondence: [email protected] 1 Department of Pathology/Molecular Pathology, Montefiore Medical Center, Albert Einstein College of Medicine, 1635 Poplar St., Bronx, NY 10461, USA Full list of author information is available at the end of the article
with different terminology such as 21q deletion syndrome, 21q- syndrome or partial 21q monosomy. The severity of the phenotype depends on the location and size of the deleted region [1]. In general, the condition leads to an increased risk of birth defects, developmental delay and intellectual deficit. Proximal and distal deletions lead to
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