Diagnosis of prenatal 22q11.2 duplication syndrome: a two-case study

The objective of the study was to perform the prenatal diagnosis of two foetuses with 22q11.2 duplication for 2.5 Mb after noninvasive prenatal testing (NIPT), and to explore the prenatal diagnosis and genetic characteristics of these foetuses. After amniocentesis, each foetus was diagnosed through karyotype analysis and single-nucleotide polymorphism array (SNP-array), and copy number variation using shotgun sequencing (CNV-seq) was carried out on each mother's peripheral blood for comparative analysis. Both pregnant woman 1 and pregnant woman 2 had foetal amniotic fluid chromosomal karyotypes of 46, XN. The SNP-array result for foetus 1 was arr[hg19] 22q11.21(18,648,856-21,800,471) x3; namely, 22q11.2 had a 3.1 Mb repeat, and the SNP-array result of foetus 2 was arr[hg19]22q11.2(18,648,855-21,464,764) x3; there was a 2.4 Mb repeat of 22q11.2. The CNV-Seq result of the peripheral blood of pregnant woman 1 was seq[hg19]22q11.2(18,953,139-21,449,967) x3; namely, in this mother's 22q11.2 region, there was ~2.5 Mb of duplicate fragment that was pathogenic to CNV. We confirmed that case 1 was inherited from the mother by CNV-seq. In both cases, however, there were key region deletions, including 41 OMIM genes such as CLTCL1, HIRA and TBX1. Both SNP-array and CNV-seq can effectively diagnose 22q11.2 duplication syndrome and clarify its fracture site and involved genes, which may facilitate understanding of the genotype and phenotype correlations.