The Trisomies

Question 1

What is the most common trisomy at birth?

Answer 1

Trisomy 21 (Down syndrome)

Question 2

What are the key clinical features of Down syndrome?

Answer 2

Intellectual disability, Flat facies, Epicanthal folds, Single palmar crease, Sandal gap toes

Question 3

What congenital heart defect is most associated with Down syndrome?

Answer 3

Atrioventricular (AV) septal defect

Question 4

What is the most common genetic cause of Down syndrome?

Answer 4

Meiotic nondisjunction (95% of cases)

Question 5

What are the other two causes of Down syndrome besides meiotic nondisjunction?

Answer 5

Robertsonian translocation (4%), Mosaicism (1%)

Question 6

What is the karyotype of Down syndrome?

Answer 6

47,XX,+21 or 47,XY,+21

Question 7

What cancers are associated with Down syndrome?

Answer 7

Acute lymphoblastic leukemia (ALL), Acute myeloid leukemia (AML, especially megakaryoblastic AML)

Question 8

What neurological disorder is associated with Down syndrome later in life?

Answer 8

Alzheimer disease (early onset due to APP gene on chromosome 21)

Question 9

What are the key first-trimester screening findings for Down syndrome?

Answer 9

Increased nuchal translucency, Hypoplastic nasal bone, Low PAPP-A, High β-hCG

Question 10

What are the second-trimester quadruple screen findings for Down syndrome?

Answer 10

↓ AFP, ↑ β-hCG, ↓ Estriol, ↑ Inhibin A

Question 11

What is the karyotype of Edwards syndrome?

Answer 11

47,XX,+18 or 47,XY,+18

Question 12

What are the key clinical features of Edwards syndrome (Trisomy 18)?

Answer 12

Rocker-bottom feet, Clenched hands with overlapping fingers, Prominent occiput, Micrognathia

Question 13

What congenital heart defect is associated with Edwards syndrome?

Answer 13

Ventricular septal defect (VSD)

Question 14

What is the prognosis of Edwards syndrome?

Answer 14

Severe intellectual disability; death usually by 1 year

Question 15

What are the second-trimester quadruple screen findings for Edwards syndrome?

Answer 15

↓ AFP, ↓ β-hCG, ↓ Estriol, ↓ Inhibin A

Question 16

What is the most common cause of Edwards syndrome?

Answer 16

Meiotic nondisjunction

Question 17

What is the karyotype of Patau syndrome?

Answer 17

47,XX,+13 or 47,XY,+13

Question 18

What are the key clinical features of Patau syndrome (Trisomy 13)?

Answer 18

Severe intellectual disability, Microcephaly, Holoprosencephaly, Cleft lip/palate, Polydactyly

Question 19

What congenital heart defects are associated with Patau syndrome?

Answer 19

Ventricular septal defect (VSD), Patent ductus arteriosus (PDA)

Question 20

What is a hallmark brain abnormality in Patau syndrome?

Answer 20

Holoprosencephaly (failure of forebrain division)

Question 21

What are common eye abnormalities in Patau syndrome?

Answer 21

Microphthalmia (small eyes), Coloboma (keyhole-shaped defect in the eye)

Question 22

What is the prognosis of Patau syndrome?

Answer 22

Death usually within the first year

Question 23

What is the most common cause of Patau syndrome?

Answer 23

Meiotic nondisjunction

Question 24

What are the first-trimester screening findings for Patau syndrome?

Answer 24

↓ β-hCG, ↓ PAPP-A, Increased nuchal translucency

Question 25

How do the quad screen results differ between Down, Edwards, and Patau syndromes?

Answer 25

Down: ↑ hCG, ↑ Inhibin A, ↓ AFP, ↓ Estriol | Edwards: All ↓ | Patau: No specific pattern but ↓ hCG, ↓ PAPP-A

Question 26

Which trisomy is most associated with holoprosencephaly?

Answer 26

Trisomy 13 (Patau syndrome)

Question 27

Which trisomy has the best survival rate?

Answer 27

Trisomy 21 (Down syndrome)

Question 28

Which trisomy is associated with a single palmar crease?

Answer 28

Trisomy 21 (Down syndrome)

Question 29

Which trisomy is associated with clenched hands and overlapping fingers?

Answer 29

Trisomy 18 (Edwards syndrome)

Question 30

Which trisomy is associated with polydactyly?

Answer 30

Trisomy 13 (Patau syndrome)