A Rare Case of Hemoglobin Bart’s Hydrops Fetalis due to Uniparental Disomy of Chromosome 16

BackgroundRecently, a patient with maternal uniparental disomy of chromosome 16 (UPD(16)mat) presenting with Silver-Russell syndrome (SRS) phenotype was reported. SRS is characterised by growth failure and dysmorphic features.ObjectiveTo clarify the prevalence of UPD(16)mat in aetiology-unknown patients with SRS phenotype and phenotypic differences between UPD(16)mat and SRS.MethodsWe studied 94 patients with SRS phenotype of unknown aetiology. Sixty-three satisfied the Netchine-Harbison clinical scoring system (NH-CSS) criteria, and 25 out of 63 patients showed both protruding forehead and relative macrocephaly (clinical SRS). The remaining 31 patients met only three NH-CSS criteria, but were clinically suspected as having SRS. To detect UPD(16)mat, we performed methylation analysis for the ZNF597:TSS-differentially methylated region (DMR) on chromosome 16 and subsequently performed microsatellite, SNP array and exome analyses in the patients with hypomethylated ZNF597:TSS-DMR.ResultsWe identified two patients (2.1%) with a mixture of maternal isodisomy and heterodisomy of chromosome 16 in 94 aetiology-unknown patients with SRS phenotype. Both patients exhibited preterm birth and prenatal and postnatal growth failure. The male patient had ventricular septal defect and hypospadias. Whole-exome sequencing detected no gene mutations related to their phenotypes.ConclusionWe suggest considering genetic testing for UPD(16)mat in SRS phenotypic patients without known aetiology.

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Case Report: Paternal Uniparental Isodisomy and Heterodisomy of Chromosome 16 With a Normal Phenotype

Frontiers in Pediatrics ◽

10.3389/fped.2021.732645 ◽

2021 ◽

Vol 9 ◽

Author(s):

Xu Zhang ◽

Li Liu ◽

Yang Liu ◽

Xin Pan

Keyword(s):

Prenatal Diagnosis ◽

Genetic Testing ◽

Genetic Diseases ◽

Molecular Genetic ◽

Uniparental Disomy ◽

Snp Analysis ◽

Chromosome 16 ◽

Pathogenic Variants ◽

First Case ◽

Whole Exome

Uniparental disomy (UPD) is a specific type of chromosomal variant that has been detected in both prenatal diagnosis and neonates with advances in molecular genetic testing technologies [mainly chromosome microarray analysis (CMA) technologies containing single-nucleotide polymorphism (SNP) probes]. In this case, we performed non-invasive prenatal genetic testing (NIPT) to screen fetuses for aneuploidy and detected the presence of aneuploidy chimerism and UPD by CMA, including SNP analysis and whole-exome sequencing, to detect pathogenic variants within the genome. The NIPT results suggested an increased number of fetal chromosome 16, and the CMA results indicated that it was the first case of holistic paternal UPD16 with isodisomy combined with heterodisomy, although no abnormal phenotype was seen in the newborn at postnatal follow-up. The homozygous region of the isodimer combined with the heterodimer is smaller than that of the complete isodimer, and it is less prone to recessive genetic diseases. A retrospective analysis of this case of paternally derived UPD16 was used to explore the uniparental diploid origin of chromosome 16 and to provide some reference for genetic counseling and prenatal diagnosis.

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