[Analysis of three families with recurrence of non-immune hydrops fetalis by trio whole exome sequencing].

OBJECTIVE To explore the genetic basis of three families with recurrence of non-immune hydrops fetalis (NIHF) but negative result by copy number variation sequencing (CNV-seq). METHODS Amniotic fluid sample and/or abortive tissues of the fetuses were collected and subjected to CNV-seq analysis. Peripheral blood samples of the parents were also taken for trio whole exome sequencing (trio WES). RESULTS Fetus 1 was found to harbor heterozygous c.976G>T(p.Glu326*) variant of the SOX18 gene in addition with compound heterozygous variants c.844C>T(p.Arg282Trp) and c.9472+1G>A of the RYR1 gene. The three variants were all inherited from its parents and have been associated with the etiology of NIHF. Based on the American College of Medical Genetics and Genomics (ACMG) standards and guidelines, the c.976G>T variant of SOX18 gene and c.9472+1G>A of RYR1 gene were predicted to be pathogenic (PVS1+PM2+PP3+PP4, PVS1+PM2+PP3), and c.844C>T variant of RYR1 gene to be likely pathogenic (PM1+PM2+PP3). Fetus 2 was found to harbor compound heterozygous variants c.6682C>T(p.Gln2228*) and c.4373_4383del(p.Val1458Alafs*63) of the PIEZO1 gene. Both variants were also inherited from its parents and are associated with the etiology of NIHF. Based on ACMG standards and guidelines, both c.6682C>T and c.4373_4383del variants of PIEZO1 gene were predicted to be pathogenic (PVS1+PM2+PP4, PVS1+PM2). Fetus 3 was found to harbor compound heterozygous variants of the TTN gene c.29860G>C(p.Asp9954His) and c.21107A>T(p.Asp7036Val), which were respectively inherited from its parents. Both variants have been strongly associated with the phenotype, though the connection between the etiology of NIHF and variants of the TTN gene remains elusive. Based on ACMG standards and guidelines, the c.29860G>C and c.21107A>T variants of TTN gene were predicted to be likely pathogenic (PM1+PM2+PP3). CONCLUSION Trio WES can improve the diagnosis rate of NIHF with a negative result by CNV-seq. Considering the urgency of prenatal diagnosis, CNV-seq and trio WES should be carried out at the same time for fetuses with NIHF.