Occurrence of fetal choroid plexus cysts in siblings: concerns regarding recurrence and chromosomal abnormality.

Choroid plexus cysts (CPC) are a well-known ultrasound aneuploidy marker easily detectable at second-trimester ultrasound examination. However, their genetic etiology is totally unknown. We report two cases of Japanese mothers who carried two and three siblings respectively; all the fetuses that had CPC were noticed at second trimester. Genetic amniocentesis revealed that each fetus had different karyotypes, that is, trisomy 18 and 46,XX in the case of one mother, and trisomy 18, 46,XY and trisomy 21 in the case of the other. These observations indicate that the genetic basis of the cysts is not linked to abnormal chromosomes. We propose that careful ultrasound observation and genetic counseling of the siblings should be offered to patients who have previously had a baby with CPC, despite that baby having a normal karyotype.