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by the American Institute of Ultrasound in Medicine J Ultrasound Med 22:425-430 • 0278-4297
Prenatal Sonographic Findings Associated With Nonmosaic Trisomy 9 and Literature ReviewDivision of Maternal-Fetal Medicine, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Medicine and Dentistry of New Jersey–Robert Wood Johnson Medical School (L.Y., R.W., S.L., A.M.V.), and Institute for Genetic Medicine, St Peter’s University Hospital (D.D.-S.), New Brunswick, New Jersey USA. Address correspondence and reprint requests to Lami Yeo, MD, Department of Obstetrics, Gynecology, and Reproductive Sciences, Division of Maternal-Fetal Medicine, University of Medicine and Dentistry of New Jersey–Robert Wood Johnson Medical School, St Peter’s University Hospital, 254 Easton Ave, Medical Office Building, Fourth Floor, New Brunswick, NJ 08903-0591 USA.
Trisomy 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 reported2; 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 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 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.
The patient was a 32-year-old Hispanic gravida 4, para 3 woman referred for routine sonography at 19.3 weeks’ menstrual age. The pregnancy was dated by a first-trimester scan. She had no notable obstetric history. The patient had been offered midtrimester serum screening but declined.
Sonography showed a fetus with growth restriction measuring 17.5 weeks overall, with the following measurements: biparietal diameter, 19.2 weeks; head circumference, 17.4 weeks; abdominal circumference, 17.3 weeks; and shortened long bones ranging between 16 and 17 weeks. The following sonographic features were observed: abnormal head shape (broad occipital area and narrowing of the parietal areas); ventriculomegaly and dangling choroid plexus; short ear length (14.3 weeks) and low-set, misshapened ears, an abnormal facial profile (sloping forehead, flat profile, small nose, and micrognathia; Fig. 1
Subsequently, she returned for fetal echocardiography at 22.4 weeks’ menstrual age. In addition to the previously identified abnormalities, this study showed an enlarged heart (occupying  40% of the chest), an atrial septal defect with a single atrium, aortic stenosis, and possible deep-set eyes. Examination for nares was difficult because of the small size of the nose. A micropenis was also visualized. The patient gave birth several days later after an induction due to intrauterine fetal death, and gross examination of the neonate confirmed low-set, malformed, small ears (they were also posteriorly rotated), abnormal facies (Fig. 3 ), camptodactyly with angulated fingers (Fig. 4), rocker-bottom feet with dorsiflexed ankles, and a micropenis, all of which were shown sonographically. Webbing of the neck and widely spaced nipples were also seen. In particular, the facies showed hypertelorism, microphthalmia, a long philtrum, an upper lip covering a receding lower lip, micrognathia, a broad, flattened nose with a small tip, and up-slanting, short palpebral fissures. The patient declined autopsy of the neonate, and birth weight was not available.
To our knowledge, only 7 cases of nonmosaic trisomy 9 that were detected specifically on prenatal sonography have been reported in the literature (Table 1 ).3,5–9 Of these cases, 1 patient interrupted the pregnancy, 1 had a spontaneous abortion, 4 had intrauterine fetal death, and 1 had neonatal death on postnatal day 24. The prognosis for complete trisomy 9 is very poor. Embryos with trisomy 9 usually have spontaneous abortion in the first trimester, and accordingly, it is rare for survival to occur to a viable gestational age. Most of these cases have low birth weight, severe perinatal asphyxia, failure to thrive, and profound growth and mental retardation.5 Neonates will usually die in the immediate neonatal period, and there is no long-term survival when complete trisomy 9 exists. McDuffie6 found that of surviving live-born infants, only 25% (3 of 12) lived beyond 1 week.
The clinical phenotype of trisomy 9 includes low birth weight, developmental delay, and abnormalities of the central nervous, craniofacial, cardiovascular, skeletal, and genitourinary systems (Table 2 ).6,8 In addition, abnormalities of these systems have also been reported on prenatal sonography. To our knowledge, only 2 cases detected on first-trimester sonography have been reported.7,9 Both had nuchal anomalies (cystic hygroma and increased nuchal translucency). One of these cases also had abnormal reversed flow in the fetal venous system, which has previously been reported to be associated with aneuploidy.10 Similar to our findings, shortened long bones were also visualized in the case of Pinette et al.7 Growth restriction appears to be a very common finding, as reported by McDuffie.6 In reviewing various reports, McDuffie6 found that of cases born after 20 weeks’ gestation, 85% (11 of 13) were small for gestational age.6 Of the trisomy 9 cases detected on sonography, including our own, 75% (6 of 8) had intrauterine growth restriction (Table 1 ).
We found the sonographic appearance of the hands to be peculiar and unique. Benacerraf et al5 first reported clenched hands in their case of trisomy 9 at 31 weeks, with rigid extension at the metacarpal–first phalangeal joints but contraction at the proximal and distal interphalangeal joints. In the case described by Roshanfekr et al,3 gross examination of the neonate’s hands (not detected sonographically) revealed findings similar to ours: hands loosely clenched in a peculiar way, with fingers flexed at the distal interphalangeal joints. The fetus in our case also had peculiarly angulated fingers on sonography that appeared to be deviated laterally (Fig. 2 ). Joint anomalies, including an abnormal position of the digits, have previously been described with trisomy 9.4 As Pinette et al7 described in their case, we also found rocker-bottom feet in our fetus.
We found cardiomegaly on sonography, and to our knowledge, this is the first report of that sonographic finding in a fetus with trisomy 9. Benacerraf et al5 found this also, but only at autopsy. Including our own case, 75% (6 of 8) of the trisomy 9 cases had cardiac anomalies detected on sonography. Congenital heart defects are known to be found clinically in 60% of patients with trisomy 9.2 Fifty percent of fetuses with trisomy 9 (including ours) had central nervous system malformations detected sonographically. Intracranial anomalies have been noted in 65% of patients with trisomy 92 and may include hydrocephalus, a Dandy-Walker malformation, and subarachnoid cysts (Table 2 The craniofacial features we visualized sonographically (sloping forehead, narrow bifrontal diameter, deep-set eyes, small nose, micrognathia, and low-set, small, malformed ears) are characteristic anatomic features of trisomy 9.4 Sandoval et al8 also detected dysmorphic facies in their case at 23 weeks. It is known that about 65% of patients with trisomy 9 have microcephaly with narrow temples, whereas microphthalmia and deep-set eyes are seen in 50%.2 Wooldridge and Zunich11 reviewed a large series of cases and found craniofacial anomalies to be present in all cases of trisomy 9. Another study that examined 15 cases of complete trisomy 9 also found craniofacial abnormalities to be present phenotypically in 100%.12 We found the head shape and facial profile to be distinctive sonographically. As a known phenotypic feature described for trisomy 9, we visualized a micropenis (shortened with a small amount of penile tissue visualized), to our knowledge the first such case reported on sonography in a fetus with trisomy 9. Assessment of the urinary system could not be made because the patient declined autopsy. It is known that urogenital abnormalities are seen in 65% of trisomy 9 cases.2 To our knowledge, this is the first report of the sonographic appearance of a large stomach and straight portal vein in a fetus with trisomy 9. The cases described in the literature, including our own, confirm that although the karyotype is important and essential for diagnosis, the presence of abnormal sonographic findings serves as important additional information that lends support to the karyotypic diagnosis of trisomy 9. Saura et al13 concluded in their review that every case of nonmosaic trisomy 9 diagnosed via amniocentesis was always associated with sonographic abnormalities.13 When we evaluated this case initially on sonography, our suspicion of fetal aneuploidy was for trisomy 18, because there was intrauterine growth restriction, an abnormal head shape, cranial findings, cardiac defects, shortened ear length, and abnormal hand posturing. Benacerraf et al5 also noted that there are often similarities among the sonographic characteristics of trisomies 9 and 18. However, although fetuses with trisomy 18 often have completely clenched hands, we found our fetus to have different hand features. Nevertheless, when fetal sonographic abnormalities are present that are indicative of trisomy 18, trisomy 9 should also be included in the differential diagnosis. Because trisomy 9 is a lethal diagnosis, it is important to make this diagnosis prenatally, inasmuch as this may affect obstetric management, including the mode of delivery. In the literature, complete trisomy 9 has been shown to be a fatal diagnosis. For instance, in the cases with a diagnosis on the basis of prenatal sonography (except for the 2 cases in which the pregnancies were terminated), all fetuses with trisomy 9 either died in utero or after birth. Detection of an abnormal karyotype is also important for providing patients with accurate information for future genetic counseling. Therefore, any pattern of sonographic malformations that includes growth restriction, central nervous system or craniofacial defects, and cardiovascular, skeletal, and genitourinary abnormalities should lead one to suspect autosomal trisomy, including trisomy 9.
Received October 15, 2002, from the Division of Maternal-Fetal Medicine, Department of Obstetrics, Gynecology, and Reproductive Sciences, University of Medicine and Dentistry of New Jersey–Robert Wood Johnson Medical School (L.Y., R.W., S.L., A.M.V.), and Institute for Genetic Medicine, St Peter’s University Hospital (D.D.-S.), New Brunswick, New Jersey USA. Revision requested November 20, 2002. Revised manuscript accepted for publication December 18, 2002.
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