[Genetic testing and analysis of 2 cases of trisomy 11 mosaicism]

Abstract

Trisomy 11 mosaicism is clinically rare, for which making diagnostic and treatment decisions can be challenging. In this study, we used noninvasive prenatal testing, chromosome karyotype analysis, chromosome microarray analysis, copy number variation sequencing and fluorescence in situ hybridization for detecting trisomy 11 mosaicism in two cases and provided them with genetic counseling. In one of the cases, the fetus with confined placental mosaicism trisomy 11 presented with severe growth restriction and a placental mosaic level of 44%, and pregnancy was terminated at 25+3 weeks of gestation. In the other case with true low-level fetal mosaicism of trisomy 11, the pregnancy continued after exclusion of the possibility of uniparental disomy and structural abnormalities and careful prenatal counseling. The newborn was followed up for more than one year, and no abnormality was found. Noninvasive prenatal testing is capable of detecting chromosomal mosaicism but may cause missed diagnosis of true fetal mosaicism. For cases with positive noninvasive prenatal testing but a normal karyotype of the fetus, care should be taken in prenatal counseling and pregnancy management.

Keywords: confined placental mosaicism; invasive prenatal testing; noninvasive prenatal testing; trisomy 11 mosaicism; true fetal mosaicism.

图 1

T11限制性胎盘嵌合病例超声图像 Ultrasound image of the CPM11. A: Fetal bowel dilatation; B: Disappearance of the diastolic blood flow spectrum; C: Decreased blood flow resistance of the middle cerebral artery.

图 2

T11 CPM胎盘验证结果：纵轴为待测样本拷贝数与参照物拷贝数之比，正常二倍体为1.0；11号染色体未达到染色体三体的水平（1.5），嵌合比例约44% Placental testing of the CPM 11. The vertical axis is the ratio of the copy number of the tested sample to the reference (the ratio of diploid is 1.0). Chromosome 11 does not reach the level of trisomy (1.5), and the mosaic level for T11 was 44%.

图 3

T11真性胎儿嵌合体染色体核型及FISH Karyotype and FISH of the true fetal mosaicism of trisomy 11. A: Karyotyping of trisomy 11 mosaicism showing 47, XN, +11 (upper) and 46, XN, i (11)(q10) (lower). B: FISH of trisomy 11. C: FISH of diploid 11.