TRISOMY 3 MOSAICISM
Complete trisomy 3 is a rare and lethal abnormality. Trisomy 3 mosaicism detected on chorionic villus sampling of a normally developed embryo is usually confined to the placenta. Confined placental mosaicismfor trisomy 3 has been associated with a normal outcome with no evidence of the trisomy in newborn blood. Trisomy 3 mosaicism has occasionally been detected on amniocentesis and has been associated with both normal outcome and a child with multiple congenital anomalies. Adverse effects of uniparental disomy for chromosome 3 have not been reported.
Diagnosis of trisomy 3 on CVS should be followed up with amniocentesis and serial ultrasound.
Trisomy 3 detected on CVS
Trisomy 3 mosaicism has been found on CVS and subsequently not found in amniocentesis or fetal cells. It is possible that confined placental mosaicism of trisomy 3 has an effect on the fetus, however to date this has not been directly reported (Hsu et al, 1997).
Sachs et al (1990) reported on 2 cases of trisomy 3 mosaicism found on CVS. In these cases the percentage of abnormal cells measured on CVS direct studies were 10% and 71%. Both pregnancies resulted in a normal outcome. Ten cases of confined placental mosaicism for trisomy 3 were reported in a large study of chromosomal mosaicism detected on CVS. The trisomy 3 findings were not confirmed in any of the ten fetuses (Hahneman & Vejerslev, 1997).
Research on CPM 3 has shown that the trisomy 3 cells are primarily of mitotic origin. There is often a high proportion of trisomy 3 cells in the trophoblast cells. (Wolstenholme, 1996; Hahneman & Vejerslev, 1997)
Trisomy 3 detected on amniocentesis
Hsu et al (1997) reviewed two reported cases of trisomy 3 mosaicism detected on amniocentesis. One case with 5% trisomy 3 cells resulted in a normal outcome. The other case, with 36% trisomy 3 cells, resulted in a child with several health concerns, including, bilateral cleft lip and palate, congenital heart defect, pulmonary stenosis, small eyes, an abnormal left ear and vertebral abnormalities. The child died at 18 months due to heart defects.
Trisomy 3 detected postnatally
Hsu et al (1997) summarized three cases of trisomy 3 mosaicism that were diagnosed postnatally. One adult with severe mental retardation, short stature and dysmorphic face, another adult with short stature, coloboma and hip dislocation, and an infant with minor dysmorphism who died at 5 months due to severe failure to thrive.
Uniparental Disomy (UPD 3)
There are no reports of imprinted genes on chromosome 3 (Ledbetter & Engel, 1995).
Link to What is UPD?
- HUGO Chromosome 3 - Chromosome 3 specific sites
Human Chromosome 3 - 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.
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 17:201-242. 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
Sachs ES, Jahoda MG, Los FJ, Pijpers L, Reuss A, Wladimiroff JW. (1990) Interpretation of chromosome mosaicism and discrepancies in chorionic villi studies. American Journal of Medical Genetics 37:268-271. PubMed
Wolstenholme J. (1996) Confined placental mosaicism for trisomies 2, 3, 7, 8, 9, 16, and 22: their incidence, likely origins, and mechanisms for cell lineage compartmentalization. Prenatal Diagnosis 16(6):511-524. PubMed