TRISOMY 5 MOSAICISM
Complete trisomy 5 is a rare and lethal abnormality. Trisomy 5 mosaicism detected on chorionic villus sampling of a normally developed embryo is usually confined to the placenta. Confined placental mosaicism for trisomy 5 has been associated with normal outcome with no evidence of the trisomy in newborn blood. Diagnosis of trisomy 5 on CVS should be followed up with amniocentesis and serial ultrasound.
Trisomy 5 mosaicism has occasionally been detected on amniocentesis and has been associated with both normal outcome and with children born with multiple congenital anomalies. Fetal blood sampling may not be helpful for detecting true trisomy 5 mosaicism, since in a past case trisomy 5 was detected in fibroblasts and not in peripheral blood (Hsu, 1997).
Trisomy 5 detected on CVS
Three cases of confined placental mosaicism for trisomy 5 were reported in a large study of chromosomal mosaicism detected on chorionic villus sampling. The findings were not confirmed in any of the fetuses (Hahnemann and Vejerslev, 1997).
Fryburg et al (1993) described a case of trisomy 5 detected on cultured CVS. Amniocentesis was normal and low level mosaic trisomy was seen in the fetus. In most cases where trisomy is found on CVS but not on amniocentesis, the outcome is normal. However, an abnormal outcome can also occur.
Trisomy 5 detected on amniocentesis
Hsu et al (1997) reviewed 5 reported cases of trisomy 5 mosaicism detected at amniocentesis. Two cases were born with health concerns. One child had was small, had a heart murmur and an ear pit. The other child also was born small with facial dysmorphism and a congenital heart defect. In both of the abnormal cases trisomy 5 was confirmed in fibroblasts. The percentage of trisomy cells in the amniocytes did not seem to predict pregnancy outcome. In one of these cases 80% of amniocytes showed trisomy 5 cells and the pregnancy resulted in a normal liveborn (Hsu et al, 1997).
Trisomy 5 mosaicism may be another example of tissue-limited mosaicism ( Sciorra et al, 1992). In one of the abnormal cases fetal blood sampling was falsely reassuring.
Uniparental Disomy (UPD 5)
There are no reports of imprinted genes on chromosome 5 (Ledbetter & Engel, 1995).
Paternal isodisomy for chromosome 5 was detected in a 2-year-old boy with Type III Spinal Muscular Atrophy (SMA), an autosomal recessive degenerative disorder of the motor neurons. No developmental abnormalities, other than those attributable to classical childhood-onset SMA, were present (Brzustowicz et al, 1994) .
Link to What is UPD?
Link to Maternal UPD 5 page
Link to Paternal UPD 5 page
- HUGO Chromosome 5 - Chromosome 5 specific sites
Human Chromosome 5 - 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.
Brzustowicz LM, Allitto BA, Matseoane D, Theve R, Michaud L, Chatkupt S, Sugarman E, Penchaszadeh GK, Suslak L, Koenigsberger MR, Gilliam TC, Handelin BL (1994) Paternal isodisomy for chromosome 5 in a child with spinal muscular atrophy. American Journal of Human Genetics 54:482-488 PubMed
Casamassima AC, Wilmot PL, Mahoney MJ, Scott RV, Shapiro LR. (1989) Trisomy 5 mosaicism in amniotic fluid with normal outcome. Clinical Genetics. 35(4):282-4. PubMed
Fryburg JS, Dimaio MS, Yang-Feng TL, Mahoney MJ. (1993) Follow-up of pregnancies complicated by placental mosaicism diagnosed by chorionic villus sampling. Prenatal Diagnosis 13(6):481-94. 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):201-42. 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
Sciorra LJ, Hux C, Day-Salvadore D, Lee ML, Mandelbaum DE, Brady-Yasbin S, Frybury J, Mahoney MJ, Dimaio MS. (1992) Trisomy 5 mosaicism detected prenatally with an affected liveborn. Prenatal Diagnosis 12(6):477-82. PubMed