Prenatal sonographic findings associated with nonmosaic trisomy 9 and literature review.

Abstract

T risomy 9 was first reported in 1973 through blood lymphocyte testing in a newborn male with multiple congenital anomalies. 1 Since that time, only approximately 30 cases of mosaic or nonmosaic trisomy 9 have been reported 2 ; therefore, this is a relatively rare chromosomal abnormality, constituting only 2.7% of all trisomic cases. 3 Nonmosaic or complete trisomy 9 is a lethal diagnosis, with most fetuses dying prenatally or during the early postnatal period. Those who survive usually have mosaic trisomy 9 and have severe motor and mental deficiencies. With mosaic trisomy 9, the prevalence and severity of malformations and mental deficiency correlate with the percentages of trisomic cells in different tissues. 4 4 Because most complete trisomy 9 cases end in spontaneous abortion in the first trimester, there is a paucity of reports regarding the prenatal sonographic findings of complete trisomy 9. To our knowledge, only 7 cases of nonmosaic trisomy 9 that were specifically detected on prenatal sonography have been reported in the literature: first trimester (n = 2), second trimester (n = 2), and third trimester (n = 3). 3,5-9 There are distinct features associated with complete trisomy 9. Clinical and sonographic findings that have been described include intrauterine growth restriction, central nervous system abnormalities, cranial and facial anomalies, skeletal defects, congenital heart defects, and urogenital abnormalities. 6.8 8 The purpose of this report is to describe the prenatal sonographic findings in a second-trimester fetus with trisomy 9 and also to review the sonographic findings of all published cases of nonmosaic trisomy 9 that were specifically detected on sonography.