Prenatal ultrasound features and genetic analysis for 17q12 microdeletion syndrome

The 17q12 microdeletion syndrome is a type of syndrome caused by a deletion of 1.4 to 1.8 Mb in the 17q12 region of the chromosome. The main clinical features of the syndrome are structural or functional abnormalities in the kidney and urethra, type 5 diabetes, and neurodevelopmental or neuropsychiatric disorders. The diverse range of phenotypes associated with 17q12 microdeletion limited clinical recognition and diagnosis. In addition, the phenotypic description of this microdeletion is mainly about postpartum. Due to the rarity of the 17q12 microdeletion itself, studies on the prenatal phenotype of the 17q12 microdeletion are limited. This study aims to analyze the prenatal ultrasound features of 17q12 microdeletion, and to investigate the possibility of genotype-phenotype relationship for providing evidence for genetic counseling in such pregnancies.

A total of 3 320 pregnant women and their fetuses were collected for the detection of chromosome copy number variation sequencing (CNV-Seq) due to different ultrasound anomalies in Xiangya Hospital of Central South University. The clinical data of pregnant women and their fetuses who were found to harbor 17q12 microdeletion were reviewed, including maternal age, fetus ultrasound findings, gestational week of the invasive procedure, CNV-Seq results, and the pregnancy outcome. CNV-Seq was tested in the parents to verify whether the abnormality was de novo or inherited. The prenatal ultrasound features and CNV-Seq test results of these 12 fetuses were analyzed and their pregnancy outcomes were followed up.

Approximately 0.36% (12/3 320) of fetuses were detected to have 17q12 microdeletion, all characterized as renal abnormalities, accounting for 4.2% (12/288) of all prenatal ultrasound with renal abnormalities, accounting for 48% (12/25) of prenatal ultrasound with renal abnormalities and pathogenic chromosomal abnormalities. The sizes of 17q12 deletion ranged from 1.4 to 1.7 Mb, and all of them included the HNF1B gene. Nine cases were de novo, 2 inherited from the mother, and 1 inherited from father. Among 12 fetuses with 17q12 deletion, 11 cases of prenatal ultrasound suggested bilateral hyperechogenic kidneys and 1 case only showed renal cyst, in which 3 fetuses with enlarged kidneys, 1 with clubfeet, and 1 with subependymal cyst. Pregnancy outcomes were available for 11 of the 12 fetuses. Of them, the parents of 9 fetuses with de novo deletion chose to terminate the pregnancy, and 2 live birth babies inherited from their mother with normal renal function had persistent renal echogenicity enhancement after birth.

Bilateral hyperechogenic kidneys show strikingly correlation with 17q12 microdeletion, suggesting the necessity of chromosome copy numbers detection for fetuses with hyperechogenic kidneys.