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Partial trisomy 20q in a fetus with hypoplastic nasal bone, mild ventriculomegaly, and short femur

Partial duplication of the long arm of chromosome 20, also known as partial trisomy 20q , is a rare condition characterized by a variety of nonspecific craniofacial, cardiac, and skeletal defects in association with different degrees of neurodevelopmental delay (Blanc et al., 2008). The diagnosis is often elusive, with most reported cases being detected in children with noncharacteristic structural and functional anomalies prompting cytogenetic analysis (Pawlowitzki et al., 1979; Sax et al., 1986; Pierquin et al., 1988; Herens et al., 1990; Waters et al., 1990; Addor et al., 2002; Grange et al., 2005; Wanderley et al., 2005; Iglesias et al., 2006; Blanc et al., 2008). To our knowledge, based on a Medline database search, the prenatal detection of this condition has not been reported previously. We describe a case of de novo partial trisomy 20q diagnosed by amniocentesis after the sonographic detection of subtle fetal anomalies in the second trimester. A 32-year-old-woman, gravida 2, para 1, presented at 27 weeks of gestation for a sonographic evaluation after the detection of minor sonographic markers of aneuploidy during the detailed second-trimester scan. There was no previous history of genetic disorders or consanguinity, and her previous pregnancy from another partner resulted in a healthy infant delivered spontaneously at term. A first-trimester sonogram at 7 1/2 weeks confirmed the dates, but no first-trimester scan for nuchal translucency thickness measurement was performed. The detailed second-trimester scan at 23 weeks had shown a male fetus with femur length below the fifth percentile for gestational age and the suspicion of a small perimembranous ventricular septal defect. At referral, a short femur, mild ventriculomegaly of 12 mm, and a hypoplastic nasal bone of 2.7 mm were demonstrated (Figure 1a). This constellation of findings was highly suspicious of trisomy 21, but a three-dimensional (3-D) sonographic evaluation of the fetal face (Accuvix XQ, Medison Co., Seoul, Korea) revealed no facial dysmorphism suggestive of