Module 6 : Chromosomal Abnormalities Flashcards
aneuploidy définition
- state of having an abnormal number of chromosomes
- 1 extra 1 less
- means bad set
trisomy defintion
- one extra complete or partial chromosome
+ 47XY
triploidy definiton
- a complete extra set of chromosomes
+ 69xxy
turners syndrome
- 45xo
- missing and x or y from paternal side
- aka monosomy
aneuploidy characteristics
- the meiotic error that causes this is called non disjunction
- when fertilization occurs the zygote either has 45 or 47 chromosomes
what is non disjunction
- a chromosome pair fails to separate during meiosis
- the sperm or oocyte has 2 copies of a particular chromosome or no copies instead of one copy in the haploid state
what is the most common live born chromosome abnormality
- trisomy 21 (Down syndrome)
what is the most common chromosome abnormality among spontaneously aborted fetus
- 45 XO
- turners syndrome
is trisomy 21 the worst trisomy
- no trisomy 18 and 13 are more severe
trisomy 21 characteristics
- cardiac abnormalities are major cause of increased mortality in infancy
- decreased intelligence
- increased risk with maternal late maternal age
- not considered lethal
- triple screen has 60% detection rate
trisomy 21 sonographic appearance
- thick nuchal fold
- heart defect (AVSD, vsd, asd, or echogenic foci in lt or rt ventricle)
- mild renal dilation (oelviectasis also alled pyelectosis) >/= 5mm
- duodenal atresia (double bubble) or TE fistula (increased AFI)
- shortened long bones (femur and humerus)
less specific trisomy 21 sonographic signs
- cystic hygroma
- non immune hydrops
- clinodactly
- echogenic bowel
- omphalocele
- mild ventriculomegaly
- sandal foot toes
trisomy 21 triple screen test
- MSAFP decreased
- B hCG increased
- UE3 decreased
trisomy 18 triple screen test
- MSAFP decreased
- B hCG decreased
- UE3 decreased
trisomy 13 triple screen test
- not detected by triple screen test
trisomy 21 quad screen
- AFP decreased
- uE3 decreased
- B hCG increased
- Inhibin A increased
what is uE3
- uncongugated estriol
what are the two biochemical markers at 1st trimester screen
- B hCG
+ free beta human chorionic gonadotropin - PAPP-A
+ pregnancy associated plasma protein A - in Down syndrome
+ BhCG increased
+ PAPP-A decreased
trisomy 18 characteristics
- aka Edwards syndrome
- ALMOST ALWAYS LETHAL OR VERY POOR PROGNOSIS
- survivors have profound mental retardation
- poor prognosis due to heart and GI abnormalities
- 2nd most common chromosome abnormality at birth
- associated with LMA
sonographic appearance of trisomy 18
- early onset of SYMMETRIC IUGR with polyhydramnious
- clenched fists and/or clinodactyly
- club feet and/or rocker bottom feet
- CPC’s
- heart defects
+ large VSD most common
trisomy 18 less specific sonographic signs
- cleft lip and or palate \+ unilateral or bilateral - omphalocele - diaphragmatic hernia - single umbilical hernia - strawberry shaped head - radial ray syndrome \+ absent radius - micrognathia - cystic hygroma - enlarged cisterna magna
trisomy 13 characteristics
- aka Patau syndrome
- survivors have profound mental retardation
- 3rd most common chromosome abnormality seen at birth
- increased risk with advanced maternal age
sonographic appearance of trisomy 13
- midline defects
- holoprosencephaly
- cleft lip and/or palate
- eyes
- absent nose or nose replaced with a proboscis
- omphalocele
- microcephaly or IUGR
trisomy 13 less specific sonographic appearance
- polydactyly
- clinodactyly
- club feet
- rocer bottom feet
- cystic hygroma
- sever heart defects
+ hypo plastic left heart
+ VSD - polycystic kidneys
- enlarged cisterna magna
triploidy characteristics
- 69xxy, 69xyy, 69xxx
- 60% fertilized with 2 sperm
- 40% fertilized of a diploid egg
- rare usually lethal
- bHCG very high (8x normal)
- partial molar pregnancy
- NOT ASSOCIATED WITH MATERNAL AGE
triploidy from father
- 90%
- over half miscarry
- large hydropic placenta
- small symmetrical IUGR
- increased hCG
triploidy from mother
- 10%
- more live births
- small placenta
- asymmetric IUGR
- 2nd trimester low hCG due to small placenta
sonographic appearance of placenta with triploidy
- large placenta with cysts
+ only with paternal triploidy - small placenta
+ with maternal triploidy
triploidy sonographic appearance
- holoprosencephaly
- genesis of the corpus allosum
- meningomyelocele
- Arnold chiari malformation and ventriculomegaly
- heart defects
- facial clefs
- syndactyly
- club feet
- cystic hygroma
- omphalocele
turners syndrome characteristics
- 45Xo
- missing one of the sex chromosomes
- all are female and sterile
- maternal age is not a factor
- most common chromosome abnormality in spontaneous abortions however live born have few life threatening anomalies and normal intellect
- 95% aborted
sonographic appearance of turners
- cystic hygroma \+ septations within - hydrops - heart defects \+ COARCTTAION of aorta - renal agensis - horseshoe kidney - pelvic kidney
