RESEARCH LETTER
Rapid aneuploidy diagnosis of trisomy 18 by array comparative genomic
hybridization using uncultured amniocytes in a pregnancy with fetal
arachnoid cyst detected in late second trimester
Chih-Ping Chen a,b,c,d,e,f,g *, Yi-Ning Su h, Shun-Long Weng i, Fuu-Jen Tsai e,j,k, Chen-Yu Chen b, Yu-Peng Liu l,m, Schu-Rern Chern c, Wen-Lin Chen b, Pei-Chen Wu b and Wayseen Wang c,n
a Department of Medicine, Mackay Medical College, New Taipei City, Taiwan
b Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Taipei, Taiwan c Department of Medical Research, Mackay Memorial Hospital, Taipei, Taiwan
d Department of Biotechnology, Asia University, Taichung, Taiwan
e School of Chinese Medicine, College of Chinese Medicine, China Medical University, Taichung, Taiwan f Institute of Clinical and Community Health Nursing, National Yang-Ming University, Taipei, Taiwan g Department of Obstetrics and Gynecology, School of Medicine, National Yang-Ming University, Taipei,
Taiwan
h Department of Medical Genetics, National Taiwan University Hospital, Taipei, Taiwan i Department of Obstetrics and Gynecology, Mackay Memorial Hospital, Hsinchu, Taiwan j Department of Medical Genetics, China Medical University Hospital, Taichung, Taiwan k Department of Medical Research, China Medical University Hospital, Taichung, Taiwan l Department of Radiology, Mackay Memorial Hospital Hsinchu Branch, Hsinchu, Taiwan m Mackay Medicine, Nursing and Management College, Taipei, Taiwan
n Department of Bioengineering, Tatung University, Taipei, Taiwan
* Correspondence to: Chih-Ping Chen, MD
Department of Obstetrics and Gynecology, Mackay Memorial Hospital 92, Section 2, Chung-Shan North Road, Taipei, Taiwan
Tel: +886-2-25433535; Fax: +886-2-25433642, +886-2-25232448 E-mail: [email protected]
A 30-year-old G2P1 woman was referred to the hospital at 22 weeks of gestation because of abnormal sonographic findings. The woman and her husband were non-consanguineous and healthy, and there was no family history of congenital heart or brain defects. Level II ultrasound revealed a singleton fetus with microcephaly (biparietal distance: 4.77 cm and head circumference: 18.35 cm, all less than 5th centile), rocker-bottom feet, a ventricular septal defect (VSD), and a 2.36 cm × 1.51 cm midline interhemispheric hypoechoic homogeneous lesion (Figure 1). Prenatal magnetic resonance imaging (MRI) confirmed the diagnosis of an arachnoid cyst and hypogenesis of cerebellar vermis (Figure 2). The corpus callosum and cerebral ventricles were normal. Amniocentesis was performed and 37 mL amniotic fluid was aspired. About 20 mL of amniotic fluid was applied for aCGH using uncultured amniocytes, and 15 mL was applied for conventional cytogenetic analysis using cultured amniocytes. Within three days, bacterial artificial chromosome (BAC)-based aCGH showed the result of trisomy 18 [arr cgh 18p11.32q23 (RP11-1150C18 RP11-87C15)×3] (Figure 3a). Fluorescence in situ hybridization (FISH) analysis of the cultured interphase amniocytes using a combination of BAC probes RP11-29G21 (18q12.3) (40,213,562-40,396,293 bp) (spectrum green) and RP11-98B6 (4q11-q12) (52,681,899-52,856,481 bp) (spectrum red) showed three green signals and two red signals consistent with the diagnosis of trisomy 18 (Figure 3b). Eight days following amniocentesis, conventional cytogenetic analysis revealed a karyotype of 47,XY,+18. The pregnancy was terminated at 23 weeks of gestation, and a 526-g male fetus was delivered with facial dysmorphism and syndactyly of the first and second toes in the left foot and syndactyly of the third and fourth toes in the right foot. Polymorphic DNA marker analysis using quantitative fluorescent polymerase chain reaction (QF-PCR) showed that trisomy 18 in this fetus was caused by a duplication of chromosome 18 of maternal origin (Figure 4).
We previously described prenatal diagnosis of aneuploidy by array-comparative genomic hybridization (aCGH) using cultured or uncultured amniocytes [1-4]. In this report, we further demonstrate that amniocentesis for genome-wide analysis using uncultured amniocytes and aCGH is a useful alternative to cordocentesis in rapid aneuploidy diagnosis in pregnancy with abnormal ultrasound findings detected in late second trimester.
diagnosis of fetal arachnoid cysts mostly in the third trimester [6-8]. However, in a few cases, the diagnosis has been made in the second trimester or even in the first trimester [6,9]. Arachnoid cysts may progressively enlarge in utero causing ventriculomegaly and may be associated with corpus callosum dysgenesis. Prenatal MRI helps to demonstrate compression of the aqueduct, communication between the cyst and the ventricles, and corpus callosum dysgenesis.
We have presented a rare occurrence of second-trimester diagnosis of trisomy 18 in association with a midline interhemispheric fetal arachnoid cyst, microcephaly, a VSD and rocker-bottom feet. Pilu et al [10] first reported prenatal diagnosis of trisomy 18 at 22 weeks of gestation in a fetus with a small arachnoid cyst in ambient cistern in association with a double-outlet right ventricle and clenched hands. Fetal arachnoid cysts can be associated with various chromosomal abnormalities. Hogge et al [11] reported partial trisomy 9q (9q22qter) and partial monosomy Xq (Xq22qter) in a fetus with an infratentorial arachnoid cyst. The fetus postnatally manifested a prominent nose, micrognathia, overlapping of the fingers and a thin-walled cyst compressing the right cerebellar hemisphere. Souter et al [12] reported a subtelomeric deletion of the distal long arm of chromosome 14, or monosomy 14q (14q32.3qter) in a fetus with tetralogy of Fallot, intrauterine growth restriction, and a midline intracranial arachnoid cyst. The infant postnatally manifested facial dysmorphism, inguinal hernias, tetralogy of Fallot, a midline arachnoid cyst and marked global developmental delay. Elbers and Furness [13] reported the association of triploidy with a fetus with an arachnoid cyst. Stein et al [14] reported prenatal diagnosis of trisomy 20 mosaicism associated with an arachnoid cyst of basal cistern. We suggest that prenatal diagnosis of arachnoid cyst, especially in association with structural abnormalities, should alert aneuploidy and prompt a cytogenetic investigation.
Acknowledgements
This work was supported by research grants NSC-96-2314-B-195-008-MY3 and NSC-97-2314-B-195-006-MY3 from the National Science Council, and MMH-E-99004 from Mackay Memorial Hospital, Taipei, Taiwan.
References
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Figure Legends
Figure 1. Prenatal ultrasound at 22 weeks of gestation reveals a 2.36 cm × 1.51 cm midline interhemispheric hypoechoic homogeneous lesion.
Figure 2. Magnetic resonance imaging (MRI) at 22 weeks of gestation shows an interhemispheric arachnoid cyst (black arrows), and hypogenesis of cerebellar vermis (white arrow) consistent with the diagnosis of Dandy-Walker variant. (A) Sagittal, (B) axial and (C) coronal views of the MRI findings.
Figure 3. (a) Bacterial artificial chromosome (BAC)-based array comparative genomic hybridization (aCGH) analysis using CMDX BAC aCGH CA3000 chips shows a duplication of chromosome 18 consistent with the diagnosis of trisomy 18.
(b) Fluorescence in situ hybridization (FISH) analysis of interphase amniocytes using BAC probes RP11-29G21 (18q12.3) (spectrum green) and RP11-98B6 (4q11-q12) (spectrum red) shows three green signals and two red signals consistent with the diagnosis of trisomy 18. Figure 4. Representative electrophoretogram of quantitative fluorescent polymerase chain reaction
(QF-PCR) assays at short tandem repeat (STR) markers for chromosome 18. With the marker D18S979, two peaks (162 bp: 174 bp) of unequal fluorescent activity from different parental alleles (paternal: maternal) with a ratio of 1:2 in the cultured amniocytes indicates a duplication of chromosome 18 of maternal origin.
