Escape-PKatrina Smith

Trainee Genetic TechnologistMerseyside and Cheshire Regional Molecular

Genetics Laboratory

Introduction

CVS received for rapid aneuploidy analysis.

Reason for referral: Exomphalus.

DNA extracted using Qiagen EZ1 robot.

CVS analysed by QF-PCR.

Molecular Genetics

Cytogenetics

Full karyotype.

Poor sample: - Bloody.- Small amount of tissue.

Cultures grown up and 2 cell lines identified.

No normal cell lines identified.

46,XX,del(18)(p11.2)[15]/46,XX,i(18)(q10)[5]

Full Karyotype: Monosomy 18p

Del(18)(p11.2)

Normal

Full Karyotype: isochromosome

i(18)(q10)

Normal

A Second Look

Looked back at QF-PCR results.

Identified an extra peak on marker D18S391.

D18S391 only marker on p arm of chromosome 18.

QF-PCR performed with chromosome 18 mulitplex on original CVS DNA.

Multiplex contains an extra p arm marker and 2 extra q arm markers.

A Second Look

Amniocentesis

Molecular received a direct prep of the amnio and DNA extracted using Instagene method.

QF-PCR using chromosome 18 multiplex.

All q arm markers diallelic: No trisomy

Extra peak on D18S391 disappears.

Both p arm markers single peaks.

QF-PCR of Amnio

Amniocentesis Full karyotype.

2 independent cultures analysed.

46,XX,del(18)(p11.2)dn

Monosomy 18p- and no evidence of isochromosome previously seen.

Results consistent with QF-PCR.

Amnio Full Karyotype

Del(18)(p11.2)

Normal

Conclusion

Final molecular report:

Original CVS sample was consistent with the presence of confined placental mosaicism; normal cell line being present in the placenta and a monosomy 18p cell line being present in the fetus.

In summary, the result of all molecular genetic analyses are consistent with the presence of a deletion of at least part of the short arm of one of the chromosome 18’s (monosomy 18p) in the fetus.

Monosomy 18p.

Deletion of the short arm of chromosome 18. There is a wide range of clinical features which can vary in

severity.

Clinical features include: • Mental retardation• Speech delay• Short statue• Holoprosencephaly• Ptosis• Behavioural disorders• Dystonia

Confirmation Pregnancy terminated. Cord stump and placental tissue received.

Lessons Learnt

This case highlighted the fact that the QF-PCR multiplex only contained 1 marker on the chromosome 18 p arm.

This was also the case for the chromosome 21 multiplex.

This is now highlighted on the analysis spreadsheet so that any possible future cases may be investigated sooner.

It also highlights the importance cell culture artefacts can have on chromosome analysis.

This case was a good example of molecular and cytogenetics working closely together.

Acknowledgments

Special thanks to:

Emma McCarthyVictoria StintonTracy Horsedal

Many thanks for everyone from the Merseyside and Cheshire Regional Molecular Genetics Laboratory.