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Trisomy 18 Nicholas Cherney

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  • 1. Trisomy 18 Nicholas Cherney

2. Discovered by John H. Edwards Extra chromosome or piece of chromosome Can be full, partial, or mosaic Second most common trisomy after trisomy21 (Downs Syndrome) Much more common in females than males 80%About Trisomy 18 3. Edwards Syndrome Trisomy EOther Names 4. Trisomy is a type of aneuploidy. Caused by nondisjunction in eithermeiosis I or meiosis II Translocation Common way of expressing an individualwith Edwards Syndrome is 47, XX, +18 Normal would be 46, XXTrisomy 18 5. Karytotype 6. Nondisjunction 7. Full trisomy 18 is when an individual has 3 copiesof chromosome 18. ~95% Mosaic trisomy 18 arises when there is an extracopy of chromosome 18 present in some cells. ~5% Partial trisomy occurs when part of chromosome18 is translocated to another chromosome Balanced or unbalanced Extremely rareTypes of trisomy 18 8. Partial Trisomy 9. Balanced vs Unbalanced 10. Clenched hands with crossed fingers Crossed legs Rocker-bottom feet Low birth weight Low-set ears Poorly developed fingernails Small head and jaw Abnormally shaped head Small sternum Many othersSymptoms 11. Signs 12. Currently there are no treatments Each case is treated differently dependingon the specific needs of the individualTreatment 13. Majority die during fetal stage and arespontaneously aborted (miscarried) Occur in about 1 in 5,000 live births. 50% of full term babies will be still born. Males having higher rates than females. 90% of infants die within 6 monthsPrognosis 14. Because trisomy 18 is caused bynondisjunction (or translocation) it cannotbe passed to offspring. Exception: partial trisomy 18Inheritance 15. Ultrasound Maternal polyhydramnio CVS (chorionic villi sampling) 10-12 weeks of pregnancy Removal of a piece of the chorionic villi Amniocentesis 15-18 weeks of pregnancy Withdraw of small volume of amniotic fluid Blood testTests 16. How does trisomy 18 occur? (2 ways) Briefly explain the 2 in-utero tests fortrisomy 18. How can trisomy be inherited?Quiz 17. http://www.slh.wisc.edu/cytogenetics/cases/aug1997/karyo.dot http://rarediseases.info.nih.gov/GARD/Disease.aspx?PageID=4&DiseaseID=6321 http://www.chromosome18.org/TheConditions/OtherConditions/tabid/518/Default.aspx http://www.trisomy18.org/site/PageServer?pagename=whatisT18_whatis http://www.ncbi.nlm.nih.gov/pubmedhealth/PMH0002626/ http://ghr.nlm.nih.gov/condition/trisomy-18 http://ghr.nlm.nih.gov/chromosome=18 http://www.emedicinehealth.com/trisomy_18_edwards_syndrome/page6_em.htm http://ghr.nlm.nih.gov/condition/trisomy-18#diagnosis http://drugline.org/medic/term/meiotic-nondisjunction/References