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Updated: Dec 28, 2025

In Vivo Functional Study of Disease-associated Rare Human Variants Using Drosophila
Published on: August 20, 2019
Discordance of cardiovascular abnormalities in a monozygotic twin pair carrying a class II 1q21.1 microdeletion
Shan-Shan Shi1, Shao-Bin Lin2, Dan-Lei Cai3
1Fetal Medicine Centre, Department of Obstetrics and Gynecology, The First Affiliated Hospital of Jinan University, Guangzhou, Guangdong 510630, China.
Objective:
We present the prenatal diagnosis of a class II 1q21.1 microdeletion in monozygotic (MZ) twins with discordant phenotypes.
Case Report:
A monochorionic diamniotic twin pair presented with discordant ultrasound anomalies; twin A had cardiovascular abnormalities, while twin B did not. No specific complications were noted in the twins during pregnancy. A single nucleotide polymorphism array revealed an identical class II 1q21.1 microdeletion inherited from a phenotypically normal mother and identified the twins as MZ. The deleted region encompassed both the proximal 1q21.1 thrombocytopenia absent radius syndrome region and the distal 1q21.1 recurrent microdeletion region. No other rare copy number variants (CNVs) were identified, and concordance was observed in the CNVs between the twins.
Conclusion:
Discordant cardiovascular abnormalities may occur in MZ twins carrying the same class II 1q21.1 microdeletion. Further studies involving discordant MZ twins are needed to determine the modifying factors of the phenotypic heterogeneity of the microdeletion.
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