Module 6: Chromosome Abnormalities Flashcards
What is aneuploidy?
A state of having an abnormal number of chromosomes
1 extra or 1 less
What does having aneuploidy generally mean?
bad set
What is triosomy?
One extra complete or partial chromosome (47xy)
What is triploidy?
A complete extra set of chromosomes (69xxy, a form of polyploidy)
What is Turner’s syndrome?
45xo, missing a x or y from paternal side (sperm).
What is another name for turners syndrome?
Monosomy
What is the meiosis error that causes aneuploidy called?
Non-disjunction
What happens during non-disjunction?
A chromosome pair failed to separate during meiosis
The sperm has which 2 pairings with aneuploidy?
- 2 copies of a particular chromosome 46 + 1 = 47
- No copies of a particular chromosome 46 - 1 = 45
What is a haploid state?
Having a equal pairing of chromosome,
23 + 23 = 46
In terms of aneuploidy, once fertilization occurs the zygote either has what?
45 or 47 chromosomes, rather than 46
Approximately how many live born infants have a chromosome abnormalities?
1 in 160
What is the most common live born chromosome abnormality?
T21 : 1 in 800 births
Most common chromosome abnormality amount spontaneously aborted fetus is what?
Turner’s syndrome 45xo
What is more severe then T21?
T18 and T13
Which chromosomal abnormalities is considered lethal?
T13 and T18
Other autosomal trisomies besides T13 an T18 are how commonly seen? And how lethal are they?
- Rarely seen
- Lethal results
What is mosaicism?
When some individuals have some chromosomes that are euploidy and the other chromosomes are normal.
What kind of abnormalities does mosaicism individuals have?
Milder form of chromosomal abnormalities
Is T21 considered lethal?
No
What abnormalities are the major cause of mortality in infancy?
Cardiac
In T21 babies, what is the ratio of cardiac and gastric anomalies seen with T21?
1/2 have cardiac and gastric anomalies?
What increases the incidence of T21?
Increases with increasing maternal age (LMA >35 years)
Quad screen has a what rate detection rate of T21?
80%
What are some T21 sonographic appearances? 9
- Thick nuchal fold >6mm
- Absent or hypoplastic nasal bone
- Heart defects (AVSD, VSD, ASD)
- Echogenic focus in one or both ventricles
- Mild renal dilatation
- Duodenal atresia or tracheoesophageal fistula
- Shorted long bones
- Club feet/ rocker bottom feet
- Radial ray
What are some things we see with mild renal dilatation in T21?
Pelvic tasks also known as pyelectosis >5mm
What is the duodenal artesia sign?
Double bubble
What is the sign for tracheoesophageal fistula?
Increased AFI
What is a Atrioventricular canal defect of AV canal? 3
- Single central valve with 5 leaflets
- No mitral or tricuspid between the atria and ventricles
- VSD
What are less specific sonographic appearances of T21? 8
- Cystic hygroma
- Non immune hydrops
- Clinodactyly
- Echogenic bowel
- Omphalocele
- Mild Ventriculomegaly
- Sandal gap toes
- Single umbilical artery
Soft markers suggest what?
A fetus could have a chromosomal abnormality
Do soft markers harm a fetus?
No
Seen alone, are soft markers considered an added risk?
No
If soft markers are seen with other soft markers, does it imply a risk of Chromosomal abnormalities?
No
What are some structural defects of the head in terms of T21? 5
- Holoprosencephaly
- Cleft lip/ palate
- Micrognathia
- Low set ears/ small ears
- Macroglossia (enlarged tongue)
Can the triple screen maternal blood test detect T13?
Not predicted with triple screen
Label the triple screen maternal blood test?
What are three things we look for in triple screen- maternal testing?
- Alpha fetoprotein
- Human chorionic gonadotropin
- Estriol
What does the quad screen look like for T21?
- MSAFP decreased
- B- hCG increased
- UE3 decreased
- Inhibin A increased
Increased Inhibin A is suggestive of what?
T21
No change in Inhibin A is suggestive of what?
T18
When are biochemical markers at 1st trimester screen looked with maternal testing? (Not weeks but the exam type?)
Nuchal translucency u/s
What is PAPP-A?
Pregnancy associated plasma protein A
What is B-hCG and PAPP-A look like for T21?
- b-hCG increased
- PAPP-A decreased
What is the prognosis of T18 or Edwards syndrome? 3
- Almost always lethal or very poor prognosis?
- 50% die in 1st two months of life
- 90% die in the 1st year of life
Survivors of T18 babies generally have what?
Profound intellectual disabilities
Why does T18 babies have such a poor prognosis?
Heart and GI abnormalities
What is the 2nd most common chromosome abnormalities at birth?
T18 or Edwards syndrome
What is the occurrence rate of T18?
1 in every 3000 - 5000 births
What is T18 associated with?
LMA
What does the Triple screen markers look like for T18 babies?
All markers are low
What are some things seen sonographically with T18? 5
- Early onset of symmetric IUGR with polyhydraminos
- Clenched fist and/ or clinodactyly
- Club feet and/or rocker bottom feet
- Choroid plexus (CPCs)
- Heart defects
What is symmetric IUGR with Polyhydraminos?
Symmetric meaning head and body are small
What is the most common heart defects of T18?
Large VSD
What are some less common sonographic appearances of T18? 10
- Cleft lip and/ or palate
- Omphalocele
- Diaphragmatic hernia
- Single umbilical artery
- strawberry shaped head
- Radial ray syndrome
- Micrognathia
- Cystic hygromas
- Enlarged cisterna magna
- Umbilical cysts
What does strawberry shaped head usually have?
Enlarged cisterna magna
Radio ray syndrome is what?
An absent radius resulting in a clubbed hand
What is the prognosis for T13? 3
- Lethal or very poor prognosis?
- 70% are stillborn
- 85% die in 1st year
What is another name for T18?
Edwards syndrome
What is another name for T13?
Patau syndrome
Survivors of T13 or pataus syndrome generally have what?
Intellectual disability
What is the 3rd most common chromosome abnormality at birth?
T13
How many live briths are affected with T13?
1 in 5000 to 10000 births
What increases the risk of T13?
Advanced maternal age
Does triple screen detect T13?
No
What are some sonographic features of T13? 6
- Holoprosencephaly
- Cleft lip and/or palate
- Eyes
- Absent nose or nose replaced with proboscis
- Omphalocele
- Microcephaly or IUGR
What are some less specific sonographic features of T13? 8
- Polydactyly
- Clinodactyly
- Club feet
- Rocker bottom feet
- Cystic hygroma
- Severe heart defects
- Polycystic kidneys
- Enlarged cisterna magna
What are some midline Holoprosencephaly abnormalities? 4
- Severe abnormality of the forebrain cleavage
- Cerebrum or prosencephalon
- Brain does not divide
- Fusion of the cerebral hemispheres and thalami
Wha rare 3 classifications of Midline Holoprosencephaly?
- Lobar (mild)
- Semilobar
- Alobar (severe)
What is the most severe Version of Holoprosencephaly?
A labor
What does Alobar holoprosencepahly look like? (How does the cortical mantle look, what is the division of the cerebral cortex, what is the shape of the ventricles, what is the status of the thalami and 3 ventricle, and what about the Falx)
- Little or no cortical mantle
- No division of cerebral cortex in hemispheres
- Single horseshoe shaped ventricle
- Fused thalami and absent 3rd ventricle
- Falx is absent
What is a semilobar holoprocencephaly? 4 (shape of the ventricle, brain mantle, thalami, and Falx and 3rd ventricle)
- Single horseshoe shaped ventricle
- Some brain mantle
- Incomplete fusion of the thalami
- Absent Falx and 3rd ventricle
What is a lobar Holoprosencephaly? (Appearance of the anterior horns, Falx, ventricle) 3
- Fused anterior horns that appears squared off
- Incomplete Falx
- A 3rd ventricle may be seen
What is Triploidy?
Having 3 complete chromosome sites
What is the fertilization ratio of Triploidy? 2
- 60% fertilized with 2 sperm
- 40% fertilization of a diploid egg
When we have fertilization with 2 sperm we have what?
Paternal or diandry
What do we think of when we have fertilzation of a diploid?
Maternal or digny
How common is triploidy?
Rare and usually lethal
What is bHCG like with Triploidy?
Markedly high (8x)
Is triploidy associated with maternal age?
No
Triploidy is considered what type of pregnancy?
Molar pregnancy
Paternal Triploidy is called what?
Dyspermy
How many individuals are Dyspermy in terms of Triploidy?
90%
What is the miscarriage rate for Dyspermy babies?
Over half
What do we see with Dyspermy babies? 3
- Large hydropic placenta
- Small symmetrical IUGR
- Increased hCG
How many triploidy cases are digyny?
10%
What does this fetus represent?
T21 baby
What does this image demonstrate?
Nuchal fold
What does this image demonstrate?
Sonographic appearance of T21 AVSD
What does this image represent?
AVSD or atrioventricular canal defect
What does this image represent?
Sonographic Appearance of T21
What does this image demonstrate?
Pelviectasis
What does this image demonstrate?
Double bleb sign or duodenal atresia
What does this image represent?
Shortened femur or humerus
What does these images represent?
Cystic hygromas
What does these images represent?
Non immune hydrops
What does this image represent?
Clinodactyly 5th finger
What does this image represent?
Echogenic bowel
What does this image demonstrate?
Omphalocele
What does this image demonstrate?
Omphalocele later in pregnancy
What does his image represent?
Hydrocephalus
What does this image represent?
Sandal gap toes
What does these images represent?
Normal vs hypoplastic nasal bone
What does these images represent?
Normal Choroid vs CPC
What does these images represent?
Hand open vs Abnormal
What does this image represent?
Strawberry shaped head and brachycephaly
What does these images represent?
Club feet and rocker bottom
What does this image represent?
Normal radius vs radial ray syndrome
What does this image represent?
Holoprosencephaly increasing in severity
1. Normal
2. Lobar
3. Semilobar
4. Alobar
What does these images represent?
Variants of the ventricle shapes in Alobar holoprosencephaly, from
1. Pancake
2. Cup
3. Ball
What does this image represent?
Alobar holoprosencephaly
What does this image represent?
Lobar Holoprosencephaly
What does these images represent?
Abnormal faces of holoprosencephaly
What does these images represent?
Microphthalmia
What does these images represent?
Cyclops and median cleft lip
In terms of maternal- mother Triploidy, what are the S/S? 2
- Asymmetric IUGR
- Small placenta
What does the hCG look like with Maternal Triploidy during 2nd trimester?
2nd trimester is low due to small placenta
What is the sonographic appearance of the placenta with Triploidy? 2
- Large placenta with cysts (only when fertilized with two sperm)
termed partial mole - Small placenta with maternal Triploidy
What is the sonographic appearance of Triploidy? 10
- Holoprosencephaly
- Agenesis of the corpus callosum
- Meningomyelocele
- Arnold chiari malformation, and Ventriculomegaly
- Heart defects
- Facial clefts
- Syndactyly
- Club feat
- Cystic hygroma
- Omphalocele
Which demographic are the turners babies?
Females
Why are turners babies sterile?
They don’t have ovaries
Is maternal age a factor of Turner’s syndrome?
No
What is the prognosis of live tuners births?
Live born 45xo have few life threatening anomalies and normal intellect
What is the therapeutic abortion rate for turners?
95%
What is the sonographic appearance of Turner’s syndrome babies? 5
- Cystic hygroma
- Hydrops
- Short limbs
- Heart defects
- Renal abnormalities
What are some heart defects of turners?
Coarctation of the aorta
What are some renal abnormalities of turners? 3
- Agenesis
- Horseshoe kidney
- Pelvic kidney
What does Noonans syndrome get compared to?
Compared to tuners because of similar characteristics
Which genders are affected by noonans?
Males and females
What are some things that we see with Noonan syndrome? 3
- Short stature
- Neck webbing
- Cardiac anomalies
What is the sonographic appearance to Noonan syndrome? 3
- Similar to tuners but identifying a male fetus indicates Noonan’s
- Cervical lymphatic drainage abnormalities producing a cystic hygroma
- Cardiac defects
What does this image represent?
Turner’s syndrome
What does this image represent?
Cystic hygroma
What does this image represent?
Turner’s syndrome baby