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)/46,XX,i(18)(q10)
Full Karyotype: Monosomy 18p Del(18)(p11.2) 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.
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.
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
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 McCarthy Victoria Stinton Tracy Horsedal Many thanks for everyone from the Merseyside and Cheshire Regional Molecular Genetics Laboratory.