A case of maternal uniparental disomy of chromosome 9 diagnosed prenatally and the related problem of residual trisomy.
Non-mosaic trisomy 9 was found in a chorionic villus (CV) sample taken from a 43-year-old woman referred for prenatal chromosome analysis due to advanced maternal age. Follow-up amniocentesis revealed level 2 mosaicism for trisomy 9. Trisomy 9 was not detected at fetal blood sampling. Molecular analysis of fetal (amniocyte) DNA showed maternal uniparental heterodisomy (UPD) for chromosome 9. Two crossovers resulted in a region of isodisomy in the distal long arm. Trisomy rescue of a meiosis 1 segregation error seems to have been responsible for the uniparental disomy of chromosome 9. The pregnancy continued and neonatal blood testing showed a mosaic trisomy 9 karyotype, i.e. 4/50 cells analysed. Clinical postnatal follow-up for a period of 1 year has documented only minor facial dysmorphism and skeletal abnormalities. Development appears unremarkable. This case is the second report of maternal uniparental disomy for chromosome 9 detected prenatally and is the first case followed up post-term. This report highlights the difficulty of making informed prognostic assessments in such cases despite extensive laboratory investigation.
Slater
H R
HR
VCGS Cytogenetics Laboratory, Murdoch Children's Research Institute, Parkville, Victoria 3052, Australia. slaterh@cryptic.rch.unimelb.edu.au
Ralph
A
A
Daniel
A
A
Worthington
S
S
Roberts
C
C
D000328:Adult; D000649:Amniocentesis; D002478:Cells, Cultured; D015193:Chorionic Villi Sampling; D002899:Chromosomes, Human, Pair 9; D004247:DNA / Q000032:analysis; D005260:Female; D005817:Genetic Counseling; D006801:Humans; D007621:Karyotyping; D008297:Male; D008423:Maternal Age; D008540:Meiosis / Q000235:genetics; D018895:Microsatellite Repeats; D009030:Mosaicism; D016133:Polymerase Chain Reaction; D011247:Pregnancy; D018566:Pregnancy, High-Risk; D014314:Trisomy
D004247:DNA