[Non-invasive prenatal testing and genetic diagnosis of a case of Pallister-Killian syndrome].

OBJECTIVE To apply combined non-invasive prenatal testing (NIPT), chromosomal karyotyping and chromosomal microarray for the screening and prenatal diagnosis of a fetus with supernumerary small marker chromosome (sSMC). METHODS Standard NIFTY and full gene NIFTY kits were applied to detect free DNA (cfDNA) isolated from peripheral blood sample of a pregnancy woman. Amniocentesis was carried out for the woman for an abnormal NIPT result. G-banded karyotyping and single nucleotide polymorphism array (SNP array) were used to determine the karyotype and copy number variants in the fetus. The result was validated with a fluorescence in situ hybridization (FISH) assay. RESULTS Both the standard NIFTY and full gene NIFTY indicated abnormal dup(chr12:707 334-33 308 759), for which the T score value of copy number anomaly in full gene NIFTY is 6.823, which is higher than the standard NIFTY's T-score value of 3.9535. The two NIFTY results were both above the normal threshold ± 3. Conventional G-banding analysis of amniocytes showed that the fetus has a karyotype of 47,XY,+mar. SNP-array delineated duplication of 12p (arr [hg19]12p13.33p11.1 (173 786_34 385 641)× 4, which was verified by FISH. Based on the above results, the fetus was diagnosed as a novel case of Pallister-Killian syndrome. CONCLUSION NIPT has a certain value for the prenatal detection of PKS. Combined use of multiple techniques can facilitate delineation of the source of sSMC.