A 46,XX,der(13;14)(q10;q10),+21 child born after a 45,XX,der(13;14)(q10;q10) chromosomal finding in CVS

Complete discrepancy between QF‐PCR analysis of uncultured villi and karyotyping of cultured cells in the prenatal diagnosis of trisomy 21 in three CVS

“…In three out of four cases, the trisomic cell line was confined to the mesenchymal core and not detected in direct preparations. Sikkema-Raddatz et al (1997) reviewed 20 published cases of discrepant karyotypes (excluding structural abnormalities) where direct karyotypes gave a 'false negative' normal result of which eight involved trisomy 21. Saura et al (1998) reported three cases of false negative trisomy 21 in 'Direct' preparations in 9000 CVS and thus estimated the risk of recurrence of false negative trisomy 21 in 'Direct' preparations at 1 : 3000.…”

“…Mosaicism may be compartmentalised within a cell lineage and may or may not be associated with a normal fetal karyotype (Kalousek et al, 1987;Simoni and Sirchia, 1994). For trisomy 21, false negative results are more prevalent in direct or short-term culture (STC), consistent with the absence of trisomic cells from the embryologically remote cytotrophoblast layer (Sikkema-Raddatz et al, 1997;Saura et al, 1998). For non-mosaic standard trisomy 13, 18 and 21, long-term culture (LTC) karyotypes are considered a reliable indicator of fetal abnormality (Smith et al, 1999).…”