Prenatal finding of a fetus with mosaicism for two balanced de novo chromosome rearrangements.

Karyotyping of a fetus with mild cerebral ventriculomegaly detected with ultrasound at 23 weeks revealed two apparently balanced structural rearrangements in mosaic form. Using conventional cytogenetics and FISH, the chromosomal constitution was identified as 46,XX,t(3;10)(p13;q21.1),inv(6)(p23q12)/46,XX. A 46,XX chromosome constitution was predominantly present in the skin whereas in the fetal blood the cell line with two balanced chromosome rearrangements was selectively retained. To the best of our knowledge this is the first prenatal case of mosaicism for two de novo balanced structural chromosome rearrangements to be reported.