Down Syndrome Flashcards
Down syndrome also called
Trisomy 21
Down syndrome frequency
1/700
Down syndrome associated diseases
- Duodenal atresia
- Hirschsprung disease
- Congenital heart disease (especially ostium primum-type ASD)
- Increased risk for ALL
- Increased risk for AML
- Increased risk for Alzheimer (>35)
Down syndrome phenotype
- Intellectual disability
- Flat facies
- Prominent epicanthal folds
- Gap between 1st 2 toes
- Brushfield spots
- Single palmar crease
Most common viable chromosomal disorder
Down syndrome
Most common cause of genetic intellectual disability
Down syndrome
Down syndrome/causes of trisomy
- 95% due to meiotic nomdisjunction of homologous chromosomes (increased with adv maternal age)
- 4% due to Robertson translocation (14 + 21)
- 1.% mosaicism (no maternal association)
Down syndrome maternal association frequencies
1: 25 if mother is over 45
1: 1500 if under 20
Second-trimester QUAD screen shows in Down syndrome
- Decreased a-fetoprotein
- Increased inhibin A
- Decreased estriol
- Increased β-hCG
First trimester findings in down syndrome
- Increased nuchal translucency (UL)
- Hypoplastic nasal bone (UL)
- Decreased serum PAPPA-A
- Increased β-hCG
Edwards syndrome also called
Trisomy 18
Edwards syndrome frequence
1/8000
Most common trisomy resulting in live birth
Down
2nd most common trisomy resulting in live birth
Edwards syndrome
Edwards syndrome age of death
Within first year
Edwards syndrome first trimester (Lab)
Decreased PAPPA-A and free β-hCG
Edward syndrome findings
- SEVERE intellectual disability
- Micrognathia (small jaw)
- Clenched hands with overlapping finbers
- Low set ears
- Congenital heart disease
- Prominent occiput
- Rocker-bottom feet
Second trimester QUAD screen show of Edward’s syndrome
- Decreased α-fetoprotein
- Decreased β-hCG
- Decreased estriol
- Decreased or normal inhibin A
Patau syndrome also called
Trisomy 13
Patau syndrome frequence
1/15000
First trimester pregnancy screen show for Platau syndrome
- Decreased free β-hCG
- Decreased PAPPA-A
- Increased nuchal translucency
Platau syndrome findings
- SEVERE intellectual finindings
- Rocker bottom feet
- Micropthalmia
- Microcephaly
- Cleft lip/Palate
- Holoprosencephaly
- Polydactyly
- Congenital heart disease
Robertsonian translocation-chromosomes involved
13, 14, 15, 21, 22
Robertsonian translocation process
The long arms of 2 acrocentric chromosomes fuse at the centromere and the 2 short arms are lost
Robertsonian tranloctiom phenotype
Balanced translocation-normal
Unbalanced translocation-miscarriage, stillbirth, chromosomal imbalance (eg Down, Patau syndrome)
Cri-du-chat syndrome process
Congenital microdeletion of short arm of chromosome 5 (46,XX or XY, 5p-)
Williams syndrome process
Congenital microdeletions of long arm of chromosome 7 (deleted region includes elastin gene)
Cri-du-chat findings
- Microcephaly
- Intellectual disability (moderate to severe)
- VSD
- Epicanthal folds
- High-pitched crying/mewing
Williams syndrome findings
- Distinctive “elfin” faces
- Intellectual disability
- Hypercalcemia (increased sensitivity to vit D)
- Well developed verbal skills
- Extreme friendliness with strangers
- Cardiovascular problems
22q11 deletion is due to
Aberrant development of 3rd and 4th BRANCHIAL POUCHES
DiGeorge syndrome
Thimic, parathyroid, cardiac defect
22q11 deletion syndromes presentation
Variablae
1. Cleft palate 2. Abnormal facies 3. Thymic aplasia (T-cell deficiency) 4. cardiac defect 5. parathyroid aplasia (Hypercalcemia) 6. DiGeorge syndrome 7. Velocardiofacial syndrome
Velocardiofacial syndrome
Palate, facial, cardiac defect
Patau syndrome/age of death
Within the first year
Dow syndrome - early onset Alzheimer - mechanism
ch21 codes for amyloid precursor protein
cardiovascular problems of Williams syndrome
Supravalvular aortic stenosis
22q11 deletion syndromes - cardiac defects
- Truncus arteriosis
2. Tetrallogy of Fallot
Ch 3 - anomalies
VHL
Ch 4 - anomalies
ADPKD (PKD2)
achondroplasia
Huntington
Ch 6 - anomalies
Hemochromatosis
Ch 7 - anomalies
Williams syndrome
CF
Ch 9 - anomalies
Friedreich ataxia
Ch 11 - anomalies
Wilms tumor
β-globulin defects (sickle, β th)
Ch 13 - anomalies
Pataw syndrome
Wilson disease
RB (RB1)
BRCA2
Ch 15 - anomalies
Prader-Willi syndrome
Angelman syndrome
Marfan
Ch 16 - anomalies
ADPKD (PKD1)
α-globulin gene defects
Ch 17 - anomalies
NF1
BRCA1
Ch 18 - anomalies
Edwards syndrome
Ch 21 - anomalies
Down syndrome
Ch 22 - anomalies
NF2
Di George syndrome (22q11)
Ch 5 - anomalies
Cri-du-chat syndrome
FAP
BRCA ch?
BRCA 1 –> 17
BRCA 2 –> 13
Neurofibromatosis genes - ch?
NF1 –> 17
NF2 –> 22
α + β glubilins - ch
α –> 16
β –> 11
Retinoblastoma - ch
11
heterochromatosis - ch
6
Friedreich ataxia - ch
9
CF - ch
FAP - ch
CF 7
FAP 5
achondroplasia - ch
4
Angelman syndrome
15