Prenatal diagnosis of trisomy 9: cytogenetic, FISH, and DNA studies

Abstract

A cytogenetic survey and follow-up studies were performed in eight cases of full, mosaic, and pseudomosaic trisomy 9 prenatally diagnosed among 36,213 prenatal samples in our department between August 1970 and July 1996. Besides conventional chromosome analysis, interphase fluorescent in situ hybridization (FISH) was employed. FISH turned out to be a rapid and accurate method for verification of trisomy cell lines and could provide additional information to the prenatal cytogenetic results. FISH also enables the study of uncultured specimens of amniotic fluid, not accessible for traditional cytogenetic analysis. In three cases, retrospective DNA analysis showed the supernumerary chromosome 9 to be of maternal origin. The disomic cell lines in both mosaic trisomy 9 cases showed maternal uniparental disomy.

Prenatal ultrasound findings in complete trisomy 9

“…Most of our cases had the diagnosis of trisomy 9 confirmed further on amniotic fluid or postnatal samples. However, pseudomosaicism or confined placental mosaicism is well recognized with trisomy 915, 20. These conditions are more likely to be found when the original cytogenetic sample is chorionic villi.…”

“…Previous groups have suggested that in every case of trisomy 9 diagnosed on chorionic villi the parents should be counseled regarding the risk of pseudomosaicism or confined placental mosaicism, and offered further fetal analysis by amniocentesis and/or fetal blood sampling and detailed ultrasound assessment15. The uncultured amniocytes or blood lymphocytes can be rapidly analyzed using fluorescent in situ hybridization for chromosome 9 as well as standard culture20. All cases of complete trisomy 9 diagnosed on amniocytes or lymphocytes have been associated with ultrasound anomalies15 and, where relevant, the option of TOP should be offered to the parents.…”

Trisomy 9 mosaic syndrome: Sixteen additional patients with new and/or less commonly reported features, literature review, and suggested clinical guidelines

“…Of spontaneous abortions caused by autosomal trisomies, approximately 2.2% to 2.7% are due to T9 (Ferreres et al, 2008), and most spontaneously abort (Ferreres et al, 2008; Patil et al, 2012; Pinette et al, 1998). Prenatally reported cases are challenging because cytogenetic abnormalities can be limited to fetal membranes (Pfeiffer et al, 1984; Saura et al, 1995; Sutherland et al, 1976), and it may be difficult to distinguish between generalized and placental mosaicism (Van den Berg et al, 1997). Additionally, many individuals with T9 were diagnosed on limited cell numbers and/or did not have additional confirmatory tissue, so low‐level mosaicism may not be excluded (Cantú et al, 1996).…”

Trisomy 9 Mosaicism Diagnosed In Utero

“…More than 50 cases have been reported, most of which were diagnosed after birth. As cases diagnosed prenatally usually culminate in induced abortions [1–4], the natural history of fetuses with trisomy 9 mosaicism remains unknown. We report three cases of trisomy 9 mosaicism diagnosed in utero with ongoing pregnancies.…”