A Case of a Fetus with a Chimeric Duplication of 9p21.1p13.1 and a Normal Pregnancy Outcome

The clinical characteristics of 9p trisomy or 9p partial trisomy syndrome are growth retardation and intellectual disability, auricular deformity, eye distance too wide, sunken eyeballs, bulbous nose, low corners of the mouth, abnormal development of hands and toes and so on.

Fetal amniotic fluid cells were detected through CNV-seq, and the results were analyzed and compared. Conventional G-banding karyotyping was used to detect fetal amniotic fluid cells and parental peripheral blood.

The CNV-seq result of amniotic fluid cells showed that about 8.60 Mb chimeric duplication in 9p21.1p 13.1, with a chimeric proportion of 26%, and the variant was classified as likely pathogenic. The karyotype result of amniotic fluid cells was 47,XN,+mar[24]/46,XN[76]. The peripheral blood karyotypes of both parents showed no apparent abnormalities. The pregnancy outcome of the fetus was normal.

The phenotype and pathogenicity of CNV mosaicism are difficult to determine. During genetic counseling, a comprehensive risk assessment should be conducted by integrating test results and literature evidence. The decision on the pregnancy outcome must be based on the principle of informed consent and respect the wishes of both parents.