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Case Reports
. 2011:2011:158086.
doi: 10.1155/2011/158086. Epub 2011 Jul 31.

Inheritance of a Ring Chromosome 21 in a Couple Undergoing In Vitro Fertilization (IVF): A Case Report

Roberto L P Mazzaschi  1 , Donald R Love, Ian Hayes, Alice George
Affiliations
Case Reports

Inheritance of a Ring Chromosome 21 in a Couple Undergoing In Vitro Fertilization (IVF): A Case Report

Roberto L P Mazzaschi et al. Case Rep Genet. 2011.

Abstract

An amniotic fluid sample from an in vitro fertilized pregnancy was referred for cytogenetic analysis based on a Down syndrome screening risk of 1 : 21. Routine cytogenetic analysis showed a nonmosaic karyotype of 46,XX,r(21)(p11.2q22.3), with partial monosomy for chromosome 21 due to a ring chromosome replacing one of the normal homologues. Detailed ultrasound scanning for the remainder of the pregnancy did not reveal any unusual findings. Parental bloods showed that the mother was mosaic for the ring 21 with a karyotype of 46,XX,r(21)(p11.2q22.3)/46,XX and the father had an unrelated Robertsonian translocation, with a karyotype of 45,XY,rob(13;14)(q10;q10). Microarray analysis of cultured amniocytes determined the extent of the deletion of chromosome 21 material in the ring. The parents were given genetic counselling, and a phenotypically normal female baby was delivered at term. This case highlights the importance of karyotyping as an initial step in the management of couples referred for in vitro fertilization.

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Figures

Figure 1
Figure 1
Normal chromosome homologues and relevant rearranged chromosomes in proband and parents; (a) shows the normal and ring chromosomes 21 of the proband; (b) Is a FISH image showing loss of telomeres on the r(21); (c) Shows the Robertsonian translocation chromosome detected in the proband's father.
Figure 2
Figure 2
Location and extent of the loss of genomic DNA on the ring chromosome 21. An ideogram of chromosome 21 and the genes that are located within the deleted region of the ring chromosome 21 are shown. Entries in the DECIPHER database (deletions are shown in red, and duplications are shown in blue), OMIM genes, and RefSeq genes are taken from the UCSC genome browser http://genome.ucsc.edu (Human Mar. 2006 (NCBI36/hg18) assembly). The deletion cases in DECIPHER have proximal breakpoints at positions 40.16 Mb (case 253457), 43.99 Mb (case 253454), and 45.35 Mb (case 2126), and that reported by Bertini et al. [4] (not shown above) starts at 43.50 Mb; all four deletions end at 46.89 Mb. The COL6A1, COL6A2, and PCNT genes are shown in red boxes. The horizontal red line with arrow heads denotes the extent of the chromosome 21 loss detected in the case reported here.
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