TRISOMY 17 MOSAICISM
Full trisomy 17 is quite rare, being found in only 0.02% of clinically recognized pregnancies (0.1% of spontaneous abortions). Complete trisomy 17 has never been reported in a live birth. Trisomy 17 mosaicism has been occasionally detected on chorionic villus sampling or amniocentesis and is usually associated with a normal outcome with no evidence of the trisomy 17 cells in newborn blood.
Trisomy 17 detected on CVS
One case of confined placental mosaicism for trisomy 17 was reported in a large study of chromosomal mosaicism detected on CVS. The trisomy 17 cells were not confirmed in the fetus (Hahneman & Vejerslev, 1997).
Trisomy 17 detected on amniocentesis
Hsu (1997) reported on 7 cases of trisomy 17 mosaicism detected in amniotic fluid. All 7 resulted in normal offspring with no postnatal evidence of trisomy 17 cells.
Genuardi et al (1999) reported on three cases of trisomy 17 mosaicism detected on amniocentesis. Two resulted in normal pregnancy outcome and postnatal development. The second case was normal despite the maternal UPD17 in her normal cells. The third pregnancy was terminated and pathological examination showed intra-uterine growth restriction (IUGR) and some minor dysmorphism. In this case, trisomic cells were confirmed in fetal skin fibroblasts.
A few additional case reports have been reported (it should be remembered that cases ending in an apparently completely normal outcome are rarely published--so these cases should not be used as evidence that these are common outcomes):
Lesca et al. 1999 described a case of trisomy 17 mosaicism in one of two bichorial biamniotic twins. Ultrasound was normal as was cord blood karyotype at birth, but skin fibroblasts showed trisomy in 76% of cells by FISH. Mild dysmorphic features and moderate neurologic involvement were observed postnatally, although prematurity may have also contributed to the outcome.
Witters et al. 2007 report 13% trisomy 17 in uncultured amniocytes and 50% in cultured cells after a routine ultrasound at 21 weeks gestational age showed fetal pleural effusion and mild cerebral ventriculomegaly. Low level trisomy was confirmed postnatally in urine and buccal cells but not in placenta or cord blood. The newborn was small (<3%ile) for dates and at 18 months showed mild dysmorphic features and was speaking only a few words.
Utermann et al. 2006 summarizes four additional cases plus reviews the literature. No outcome was available in case 1 (pregnancy terminated). Case 2 was diagnosed only on CVS (amniocentesis declined) and had a normal outcome. Case 3 was diagnosed on amniopcetesis and ultrasound findings showed nuchal thickening at 14 weeks, and subsequent ultrasounds showed IUGR, single umbillical artery, and foot position abnormalities. Postnatally, minor facial and a variety of other abnormalities were noted with global developmental delay. Case 4, also diagnosed on amniocentesis with IUGR noted during pregnancy and delivery at 33 weeks. A number of malformations were noted.
Trisomy 17 detected postnatally
Shaffer et al. (1996) present a case of mosaic trisomy 17 in a male presenting with mental retardation, seizures, attention deficit hyperactivity and autistic disorders, hearing loss, growth retardation, microcephaly, and minor anomalies. Although peripheral blood lymphocyte chromosomes were normal, trisomy 17 was present in the skin fibroblasts. The trisomy was of paternal origin.
Uniparental Disomy (UPD 17)
One case of UPD17 was reported with no obvious abnormalities at birth (Genuardi et al. 1999). There are no reports of imprinted genes on chromosome 17 (Ledbetter & Engel, 1995).
Link to What is UPD?
- HUGO Chromosome 17 - Chromosome 17 specific sites
Human Chromosome 17 - Provides links to gene maps, sequences, associated genetic disorders, nonhuman genetic models, identified genes, research efforts and laboratories, and other information as available. Links are very scientific.
Butler MG. (1999) Trisomy 17 mosaicism in a four-year seven-month-old girl: follow-up report. Prenatal Diagnosis 19:689-690 PubMed
Djalali M, Barbi G, Mueller-Navia J, Schneider M, Tettenborn U, Trautmann U, Ulmer R, Wolf M, Vogel W. (1998) Further observations of true mosaic trisomy 17 ascertained in amniotic fluid cell cultures. Prenatal Diagnosis 18(11):1191-1194 PubMed
Genuardi M, Tozzi C, Pomponi MG, Stagni ML, Della Monica M et al. (1999) Mosaic trisomy 17 in amniocytes: phenotypic outcome, tissue distribution, and uniparental disomy studies. Eur J Hum Genet 7(4):421-6. PubMed
Hahnemann JM, Vejerslev LO. ( 1997) European collaborative research on mosaicism in CVS (EUCROMIC)--fetal and extrafetal cell lineages in 192 gestations with CVS mosaicism involving single autosomal trisomy. American Journal of Medical Genetics 70(2):179-87. PubMed
Hsu LY, Yu MT, Neu RL, Van Dyke DL, Benn PA, Bradshaw CL, Shaffer LG, Higgins RR, Khodr GS, Morton CC, Wang H, Brothman AR, Chadwick D, Disteche CM, Jenkins LS, Kalousek DK, Pantzar TJ, Wyatt P. (1997) Rare trisomy mosaicism diagnosed in amniocytes, involving an autosome other than chromosomes 13, 18, 20, and 21: karyotype/phenotype correlations. Prenatal Diagnosis 17(3):201-242 PubMed
Ledbetter DH, Engel E. (1995) Uniparental disomy in humans: development of an imprinting map and its implications for prenatal diagnosis. Human Molecular Genetics 4:1757-1764 PubMed
Lesca G, Boggio D, Bellee V, Magaud J-P, Till M (1999) Trisomy 17Nassar AH, Chakhtoura N, Martin D. (2000) Update on prenatal diagnosis of true mosaic trisomy 17 in amniocyte cultures. Prenatal Diagnosis 20(6):521-522 PubMed
Nassar AH, Chakhtoura N, Martin D (2000) Update on prental diagnosis of true mosaic trisomy 17 in amniocyte cultures Prental Diag 20:517-525.
Shaffer LG, McCaskill C, Hersh JH, Greenberg F, Lupski JR (1996) A clinical and molecular study of mosaicism for trisomy 17. Human Genetics 97(1):69-72. PubMed
Uterman B, et al. (2006) Pre- and Postnatal Findings in Trisomy 17 mosaicism (2006)Am J Med Genet Part A: 140A:1628-1636.
Witters I, Cannie M, Fryns J-P (2007) Prenatal Diagnosis of trisomy 17 mosaicism. Prenatal Diag 27:677-678