Prenatal diagnosis and pedigree analysis in a pregnant women with fetal hyperechogenic kidneys during the third trimester

Objective To investigate the prenatal diagnosis of fetal hyperechogenic kidneys in the third trimester and conduct pedigree analysis. Methods The patient was a 33 year-old woman. In May 2017, she referred to our Prenatal Diagnosis Center because of fetal hyperechogenic kidneys detected by ultrasound examination. By sampling fetal cord blood, blood biochemical test, karyotype analysis, chromosome microarray analysis (CMA) and whole exome sequencing (WES) were performed. After identifying the pathogeny, four members of the family were investigated and their peripheral blood was tested. Results Biochemical test of cord blood showed that the creatinine was 104.5μmol/L (53-106μmol/L), and urea was 8.93 mmol/L (3.51-3.51 mmol/L); CMA test showed that 17q12 (34822465-36350028)×1 with deletion of segments of 1.5Mb, containing HNF1 - beta (189907), PIGW (610275)and another 17 OMIM genes, which was associated with 17q12 microdeletion syndrome. Fetal karyotype analysis result was normal.High-throughput gene sequencing showed that the pregnant woman had 17q12×1 deletion of 1.5 Mb, meanwhile 16 p13. 11×1 was found with deletion of 800 KB fragments. CMA results of her husband and her parents were normal. The whole sequencing identified compound heterozygous mutations in PKHD1, containing c.6794A＞ T and c.5601-8C＞ T. The former was nonsense mutation, inherited from husband, and the latter was predicted to affect splicing, inherited from the patient. Conclusion Biochemistry test of cord blood should be performed when fetal hyperechogenic kidneys are found by ultrasound in the third trimester. 17q12 microdeletion syndrome is one of the etiologies of fetal hyperechogenic kidneys. CMA, WES and pedigree analysis should be chosen to screen etiology, so that comprehensive and detailed genetic counseling will be given.