Fetal trisomy 8 mosaicism associated with truncus arteriosus Type I

In contrast to complete trisomy 8, which occurs in 0.8% of spontaneous pregnancy losses and is usually lethal, trisomy 8 mosaicism (Warkany syndrome 2), occurs in between 1:25,000 and 1:50,000 births and entails a widely variable phenotype including central nervous, ocular, cardiac, gastrointestinal, genitourinary and musculoskeletal abnormalities. Individuals with trisomy 8 mosaicism may exhibit developmental delays and are at increased risk of developing leukemia and myelodysplastic syndrome. We present an unusual case in which midtrimester sonographic diagnosis of fetal truncus arteriosus type I at 18 weeks' gestation, led to amniocentesis with an initial normal karyotype. Microarray analysis detected fetal trisomy 8 mosaicism. Systematic literature search reveals that the association between truncus arteriosus and trisomy 8 mosaicism has not been reported previously.