Module 6 : Chromosomal Abnormalities

Question 1

aneuploidy définition

Answer 1

• state of having an abnormal number of chromosomes
• 1 extra 1 less
• means bad set

Question 2

trisomy defintion

Answer 2

• one extra complete or partial chromosome

+ 47XY

Question 3

triploidy definiton

Answer 3

• a complete extra set of chromosomes

+ 69xxy

Question 4

turners syndrome

Answer 4

• 45xo
• missing and x or y from paternal side
• aka monosomy

Question 5

aneuploidy characteristics

Answer 5

• the meiotic error that causes this is called non disjunction
• when fertilization occurs the zygote either has 45 or 47 chromosomes

Question 6

what is non disjunction

Answer 6

• 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

Question 7

what is the most common live born chromosome abnormality

Answer 7

• trisomy 21 (Down syndrome)

Question 8

what is the most common chromosome abnormality among spontaneously aborted fetus

Answer 8

• 45 XO

- turners syndrome

Question 9

is trisomy 21 the worst trisomy

Answer 9

• no trisomy 18 and 13 are more severe

Question 10

trisomy 21 characteristics

Answer 10

• 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

Question 11

trisomy 21 sonographic appearance

Answer 11

• 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)

Question 12

less specific trisomy 21 sonographic signs

Answer 12

• cystic hygroma
• non immune hydrops
• clinodactly
• echogenic bowel
• omphalocele
• mild ventriculomegaly
• sandal foot toes

Question 13

trisomy 21 triple screen test

Answer 13

• MSAFP decreased
• B hCG increased
• UE3 decreased

Question 14

trisomy 18 triple screen test

Answer 14

• MSAFP decreased
• B hCG decreased
• UE3 decreased

Question 15

trisomy 13 triple screen test

Answer 15

• not detected by triple screen test

Question 16

trisomy 21 quad screen

Answer 16

• AFP decreased
• uE3 decreased
• B hCG increased
• Inhibin A increased

Question 17

what is uE3

Answer 17

• uncongugated estriol

Question 18

what are the two biochemical markers at 1st trimester screen

Answer 18

• B hCG
  + free beta human chorionic gonadotropin
• PAPP-A
  + pregnancy associated plasma protein A
• in Down syndrome
  + BhCG increased
  + PAPP-A decreased

Question 19

trisomy 18 characteristics

Answer 19

• 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

Question 20

sonographic appearance of trisomy 18

Answer 20

• 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

Question 21

trisomy 18 less specific sonographic signs

Answer 21

- 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

Question 22

trisomy 13 characteristics

Answer 22

• aka Patau syndrome
• survivors have profound mental retardation
• 3rd most common chromosome abnormality seen at birth
• increased risk with advanced maternal age

Question 23

sonographic appearance of trisomy 13

Answer 23

• midline defects
• holoprosencephaly
• cleft lip and/or palate
• eyes
• absent nose or nose replaced with a proboscis
• omphalocele
• microcephaly or IUGR

Question 24

trisomy 13 less specific sonographic appearance

Answer 24

• polydactyly
• clinodactyly
• club feet
• rocer bottom feet
• cystic hygroma
• sever heart defects
  + hypo plastic left heart
  + VSD
• polycystic kidneys
• enlarged cisterna magna

Question 25

triploidy characteristics

Answer 25

- 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

Question 26

triploidy from father

Answer 26

- 90% - over half miscarry - large hydropic placenta - small symmetrical IUGR - increased hCG

Question 27

triploidy from mother

Answer 27

- 10% - more live births - small placenta - asymmetric IUGR - 2nd trimester low hCG due to small placenta

Question 28

sonographic appearance of placenta with triploidy

Answer 28

- large placenta with cysts + only with paternal triploidy - small placenta + with maternal triploidy

Question 29

triploidy sonographic appearance

Answer 29

- holoprosencephaly - genesis of the corpus allosum - meningomyelocele - Arnold chiari malformation and ventriculomegaly - heart defects - facial clefs - syndactyly - club feet - cystic hygroma - omphalocele

Question 30

turners syndrome characteristics

Answer 30

- 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

Question 31

sonographic appearance of turners

Answer 31

``` - cystic hygroma + septations within - hydrops - heart defects + COARCTTAION of aorta - renal agensis - horseshoe kidney - pelvic kidney ```