VP16.18: Prenatal diagnosis and sonographic findings of non-mosaic 9p tetrasomy

Non-mosaic tetrasomy 9p is supernumerary isochromosome 9p and a very rare chromosome abnormality. Non-mosaic cases are poor prognosis and show multiple anomalies. A 41-year-old primigravida woman was referred to our hospital at 24 weeks of gestation. Sonographic findings were revealed fetal following multiple anomalies: bilateral mild ventriclomegaly, Dandy Walker malformation, agenesis of corpus callosum, arachnoid cyst, facial dysmorphism of bulbous nose, ear malformations (low set ear and cupped ear), and bilatral cleft lip, congenital left diaphragmatic hernia, congenital heart disease (perimembranous VSD), short finger, rocker bottom foot and fetal growth restriction. She underwent amniocentesis at 28 weeks of gestation and revealed a result of 47, XY, +idic (9) (q21.1). A 1996g male infant was delivered by Caesarean section at 37 weeks of gestation because of postoperative uterine myomectomy. Apgar scores were 5 and 8 at 1and 5 minutes, respectively. Her infant underwent an operation of CDH at 3 days after birth, tracheostomy at 57 after birth. These anomalies are common among fetuses with Trisomies 13 and 18. However, it was difficult to diagnose non-mosaic tetrasomy 9p and impractical to suspect this condition based on ultrasound study alone. These sonographic findings show common trisomies except for arthrogryposis. We require consideration of other rare chromosomal disorder and recommend genetic testing to provide information to the family about postnatal prognosis predictions.