A very complex and rare cytogenetic finding of a patient with two balanced chromosomal rearrangements involving one chromosome 1, one chromosome 6 and one chromosome 4.

Vanessa McLaughlin1, Paula Lall1, Louise Hills1, Sorour Voghoei1, Dao Nguyen1, Michael Cronin1, Amber Boys1, Fiona Norris1, David Francis1, Martin Delatycki1

1VCGS, Level 4 MCRI Building, Royal Children’s Hospital, Flemington Rd, Parkville, 3052

Microarray analysis and FISH testing were requested on an amniotic fluid sample with clinical indications of 1:7 risk of T21 on combined serum testing (CST), NF 4.0mm and low risk NIPT. The X, Y, 18, 13, 21 aneuploid FISH panel showed a normal male signal pattern. The SNP microarray analysis showed a male molecular karyotype with an interstitial deletion of approximately 6.9 megabases from chromosome region 1q42.13q42.3 and an interstitial duplication of approximately 4.7 megabases from chromosome region 4q28.3. Parental blood samples were requested for both microarray and conventional chromosome analysis to determine the origin and significance of this finding.

Microarray analysis of both the maternal and paternal blood samples were normal, with no evidence of the deletion or duplication found in the amniotic fluid sample. However, a complex rearrangement between chromosomes 1, 4 and 6 was identified by conventional chromosome analysis in the father. This complex rearrangement involved a balanced reciprocal translocation between the short arm of one chromosome 1 and the long arm of one chromosome 6, and a balanced interstitial exchange of material between the long arm of the derivative chromosome 1 and the long arm of one chromosome 4. Metaphase FISH analysis was performed using BAC probes to confirm this finding.

This patient therefore carries two balanced chromosomal rearrangements, which is a very rare cytogenetic finding.

Upon learning of this finding, this couple requested cytogenetic testing for their 2 year old son with developmental delay. Microarray analysis showed the same unbalanced pattern of inheritance found in the couple’s original prenatal sample.

 


Biography

Vanessa McLaughlin has been working in the Cytogenetics department at VCGS since 2008 and is currently a Team Leader in the Prenatal and FISH sections. Vanessa has extensive experience in conventional chromosome analysis and FISH analysis.

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