Discordance of cardiovascular abnormalities in a monozygotic twin pair carrying a class II 1q21.1 microdeletion.

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.

[Quantitative analysis of cerebellar vermis in fetuses with Dandy-Walker syndrome with three-dimensional ultrasonography].

OBJECTIVE: To evaluate the third plane image of the three-dimensional sonography (3D US) for the quantitative analysis of the cerebellar vermis in normal and Dandy-Walker syndrome (DWS) fetuses. METHODS: The cerebellar vermis was scanned with trans-abdominal 3D US in the second and third trimesters in 571 normal fetuses and 39 fetuses with Dandy-Walker syndrome. The surface area of the vermis in the mid-sagittal view was measured and calculated. The correlation between the vermian area and the pregnant week was analyzed. The data of vermian area between normal and DWS fetuses was compared. RESULTS: The vermian area was measured in 529 normal fetuses in the third plane of 3D US. The vermis grew in a linear fashion throughout pregnancy and the growth pattern positively correlated with the gestational age (r2 = 0. 854, P < 0.05). In 39 fetuses with DWS, including 14 with Dandy-Walker malformation (DWM) and 25 with Dandy-Walker variant (DWV), no vermian structure was showed in the mid-sagittal plane in 12 fetuses with DWM and 2 fetuses with DWV, whereas a small vermis appeared in other DWSs. CONCLUSIONS: The third plane image obtained by 3D US is valuable in studying the fetal cerebellar vermis during the middle and late pregnancy. Knowledge of normal and abnormal vermian appearance may help identify developmental anomalies. Measurement of vermian area in the third plane with 3D US provide a quantitative indicator for prenatal diagnosis of DWS.