Prenatal diagnosis of 9q34.3 microdeletion-associated Kleefstra syndrome in a pregnancy complicated by polyhydramnios: A case report and literature review.

Objective: Kleefstra Syndrome (KS) is a rare genetic disorder caused by a deletion at 9q34.3. Studies showed that various heart defects are observed in 41-43% of patients and abnormal features on brain imaging in 58-63%. To date, the prenatal phenotype in KS has yet to be defined.

Case Report: We present the first prenatal diagnosis and chromosomal microarray analysis (CMA) of a case of 9q34.3 microdeletion in a fetus with increased amniotic fluid, supported by abnormal prenatal ultrasound findings, and confirmed via autopsy. CMA revealed a 2.1 Mb 9q34.3 microdeletion encompassing an OMIM gene of EHMT1, which is consistent with the diagnosis of Kleefstra syndrome and 9q subtelomeric deletion syndrome.

Conclusion: When a fetus with normal karyotype presents with polyhydramnios or abnormalities noted during second-trimester prenatal ultrasound screening, CMA analysis can be considered as the next step to rule out or confirm the diagnosis of chromosomal or other genetic aberrations.