An infant with trisomy 9 mosaicism presenting as a complete trisomy 9 by amniocentesis |
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| Authors: | David M. Sherer MD Nancy Wang Howard O. Thompson Jeanne C. Peterson Marvin E. Miller Leon A. Metlay Jacques S. Abramowicz |
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| Affiliation: | Department of Obstetrics and Gynecology, Division of Maternal—Fetal Medicine and Department of Pediatrics, Division of Pediatric Genetics, and Department of Pathology, Strong Memorial Hospital, The University of Rochester School of Medicine and Dentistry, Rochester, New York, U.S.A. |
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| Abstract: | We present a case in which amniocentesis performed at 33 weeks' gestation because of symmetrical intrauterine growth retardation and decreased amniotic fluid volume led to the prenatal diagnosis of a fetus with a karyotype of 47,XX,+9, t(1;20)(q42;p11.2) pat, i.e., with an extra chromosome 9 and a balanced translocation between chromosomes 1 and 20. At delivery, the baby showed clinical features of trisomy 9, yet chromosome analysis of the cord blood revealed no trisomy 9 cells, a finding confirmed by neonatal blood karyotyping. The balanced translocation was present in all cells. A skin biopsy confirmed trisomy 9 mosaicism with 10 per cent trisomy 9 cells. The baby died at 6 weeks and an autopsy was obtained. Chromosome analysis of different organs demonstrated different frequencies of the mosaicism of trisomy 9. The possible underlying mechanism for the discrepancy between the karyotype results by amniocentesis and those of other tissues is discussed. |
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| Keywords: | Trisomy 9 mosaicism Prenatal diagnosis Amniocentesis |
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