Objective: To study the clinical characteristics and genetic variants in a family with non-immune hydrops fetalis.
Methods: Peripheral blood samples were collected from a pregnant woman with suspected non-immune hydrops fetalis of the fetus for routine blood analysis, Rh typing and TORCH test. Amniotic fluid sample was collected for G-banded chromosomal karyotyping. The genomic DNA of the proband was extracted for analysis of chromosomal abnormalities using copy number variation sequencing. Whole-exome sequencing (Trios-WES) was performed on Illumina NovaSeq 6000 platform and exonic DNA was enriched using Agilent Sure Select XT Human All Exon V6. Sorting intolerant from tolerant (SIFT), I-mutant2, PolyPhen-2 and PROVEAN were used to predict the potential effects of amino acid substitution on protein function and splicing variation. The spatial structure of codanin-1 was modeled and visualized with Alpha Fold 2 and PyMOL 2.3 software, and the variants with potential clinical significance were confirmed by Sanger sequencing.
Results: Fetal ultrasound at 17 weeks of gestation showed extensive subcutaneous edema, ascites, pleural effusion, enlarged liver and spleen, thickened placenta and pericardium defect. NGS reveals that proband has carried c.2140C>T, p.R714W, and c.1264_1265delCT, p.L422* compound heterozygous variants of CDAN1 gene, which were found to be pathogenic and inherited from proband's father and mother respectively.
Conclusion: We identified a novel heterozygous CDAN1 gene mutation causing fetal-onset congenital dyserythropoietic anemia type 1, which triggers non-immune hydrops fetalis.
目的: 对一例因不明原因胎儿期水肿的流产组织进行临床和遗传学分析，为该家系产前诊断以及遗传咨询提供可靠的理论依据。
方法: 采集孕妇外周血进行血常规、Rh血型和TORCH检测。采集羊水细胞用于细胞培养和G显带核型分析。提取胎儿引产组织基因组DNA行全基因组拷贝数变异测序; 采用Agilent's SureSelect XT Human All Exon V6进行文库制备和外显子捕获, 并使用Illumina NovaSeq 6000对胎儿及其家系成员DNA行全外显子组测序（trios-WES），并利用SIFT、I-mutant2、PolyPhen-2及PROVEAN生物信息学软件对变异位点进行蛋白功能预测。利用Alpha Fold 2和PyMOL软件对CDAN1的结构进行建模和可视化分析; 用Sanger测序对先证者及家系成员进行突变检测和验证。
结果: 胎儿17周超声提示胎儿全身皮下广泛水肿，右侧胸腔大量积液，肝脾增大，胎盘增厚，心包缺损。染色体核型分析检测和染色体拷贝数变异测序结果均正常; 全外显子组测序显示CDAN1基因：c.2140C>T（p.Arg714Trp）和c.1264_1265delCT（p.Leu422Glyfs*16）复合杂合突变，分别来自先证者父亲和母亲，生物信息学预测为可能致病性突变，对应的疾病为先天性红细胞生成障碍性贫血1型。
结论: 全外显子组测序结果显示，该胎儿为先天性红细胞生成障碍性贫血（CDAN1基因突变）导致的胎儿期非免疫性水肿，其中CDAN1基因c.1264_1265delCT为首次报道的突变。
Keywords: CDAN1; congenital dyserythropoietic anemia type 1; non-immune hydrops fetalis; whole-exome sequencing.