A case report of prenatally diagnosed tetrasomy 18 p

Two copies of the p arm of the 18 chromosome form a rare genetic disorder called isochromosome 18p or 18p tetrasomy. This genetic malformation is found in approximately 1:140 000 live births but like other chromosomal malformations is probably more frequent in 1 trimester fetuses. Since no specific 1 trimester sonographic features for this disease have been reported to date, such a rare chromosomal malformation may present a real diagnostic challenge in the routine ultrasound-based screening at 11 weeks + 0 days to 13 weeks + 6 days of gestation. Here, we report a case of fetal tetrasomy 18 detected prenatally in a 40 years old woman G8P6. A routine first trimester scan revealed no apparent fetal abnormalities but due to maternal age and low serum concentrations of placental proteins PAPP-A and free beta hCG amniocentesis was performed at 15 weeks of gestation. Conventional karyotyping and fluorescence in situ hybridization confirmed fetal 18p tetrasomy. The only complication of the procedure was fetal bradycardia of 100 bpm, however 3 minutes after the procedure, but fetal heart rate returned to normal values after 5 minutes and remained stable at 140 bpm 40 minutes following the amniocentesis. Unfortunately, after 2 weeks fetal death occurred and was confirmed during ultrasound 18 week scan. Despite several genetically induced malformations in other children of this family, the parental karyotypes were not determined due to the lack of their agreement to genetic testing and no further reproductive plans.