Resorbed co-twin as an explanation for discrepant chorionic villus results: non-mosaic 47,XX,+16 in villi (direct and culture) with normal (46,XX) amniotic fluid and neonatal blood.
Non-mosaic trisomy 16 was observed in chorionic villus cytotrophoblasts (direct) as well as cultured mesenchymal core cells derived from the pregnancy of a 38-year-old woman. Chromosome preparations from amniotic fluid and neonatal cultures (cord blood) were 46,XX. Normal fetal growth as determined by serial ultrasound examinations occurred throughout the pregnancy, which resulted in a healthy 2724 g female. Multiple biopsies taken from the umbilical cord, placental cotyledons, and fetal membranes were 46,XX. However, a placental nodule and three of six cultures initiated from membranes (amnion and chorion) showed 46,XX/47,XX,+16 mosaicism. We propose that the trisomy 16 cells arose from residual villi derived from a trisomic co-twin that never developed. This case further demonstrates that normal fetal growth may presage normal outcome irrespective of cytogenetic findings in cytotrophoblasts (direct) and cultured mesenchymal core cells.
Tharapel
A T
AT
Department of Pediatrics, University of Tennessee, Memphis 38163.
Elias
S
S
Shulman
L P
LP
Seely
L
L
Emerson
D S
DS
Simpson
J L
JL
D000328:Adult; D000653:Amniotic Fluid / Q000166:cytology*; D015193:Chorionic Villi Sampling; D002885:Chromosomes, Human, Pair 16; D005260:Female; D005312:Fetal Blood / Q000032:analysis*; D005313:Fetal Death; D005327:Fetal Resorption; D006801:Humans; D011247:Pregnancy; D014314:Trisomy; D014427:Twins