The Trisomies Flashcards
What is the most common trisomy at birth?
Trisomy 21 (Down syndrome)
What are the key clinical features of Down syndrome?
Intellectual disability, Flat facies, Epicanthal folds, Single palmar crease, Sandal gap toes
What congenital heart defect is most associated with Down syndrome?
Atrioventricular (AV) septal defect
What is the most common genetic cause of Down syndrome?
Meiotic nondisjunction (95% of cases)
What are the other two causes of Down syndrome besides meiotic nondisjunction?
Robertsonian translocation (4%), Mosaicism (1%)
What is the karyotype of Down syndrome?
47,XX,+21 or 47,XY,+21
What cancers are associated with Down syndrome?
Acute lymphoblastic leukemia (ALL), Acute myeloid leukemia (AML, especially megakaryoblastic AML)
What neurological disorder is associated with Down syndrome later in life?
Alzheimer disease (early onset due to APP gene on chromosome 21)
What are the key first-trimester screening findings for Down syndrome?
Increased nuchal translucency, Hypoplastic nasal bone, Low PAPP-A, High β-hCG
What are the second-trimester quadruple screen findings for Down syndrome?
↓ AFP, ↑ β-hCG, ↓ Estriol, ↑ Inhibin A
What is the karyotype of Edwards syndrome?
47,XX,+18 or 47,XY,+18
What are the key clinical features of Edwards syndrome (Trisomy 18)?
Rocker-bottom feet, Clenched hands with overlapping fingers, Prominent occiput, Micrognathia
What congenital heart defect is associated with Edwards syndrome?
Ventricular septal defect (VSD)
What is the prognosis of Edwards syndrome?
Severe intellectual disability; death usually by 1 year
What are the second-trimester quadruple screen findings for Edwards syndrome?
↓ AFP, ↓ β-hCG, ↓ Estriol, ↓ Inhibin A
What is the most common cause of Edwards syndrome?
Meiotic nondisjunction
What is the karyotype of Patau syndrome?
47,XX,+13 or 47,XY,+13
What are the key clinical features of Patau syndrome (Trisomy 13)?
Severe intellectual disability, Microcephaly, Holoprosencephaly, Cleft lip/palate, Polydactyly
What congenital heart defects are associated with Patau syndrome?
Ventricular septal defect (VSD), Patent ductus arteriosus (PDA)
What is a hallmark brain abnormality in Patau syndrome?
Holoprosencephaly (failure of forebrain division)
What are common eye abnormalities in Patau syndrome?
Microphthalmia (small eyes), Coloboma (keyhole-shaped defect in the eye)
What is the prognosis of Patau syndrome?
Death usually within the first year
What is the most common cause of Patau syndrome?
Meiotic nondisjunction
What are the first-trimester screening findings for Patau syndrome?
↓ β-hCG, ↓ PAPP-A, Increased nuchal translucency
How do the quad screen results differ between Down, Edwards, and Patau syndromes?
Down: ↑ hCG, ↑ Inhibin A, ↓ AFP, ↓ Estriol | Edwards: All ↓ | Patau: No specific pattern but ↓ hCG, ↓ PAPP-A
Which trisomy is most associated with holoprosencephaly?
Trisomy 13 (Patau syndrome)
Which trisomy has the best survival rate?
Trisomy 21 (Down syndrome)
Which trisomy is associated with a single palmar crease?
Trisomy 21 (Down syndrome)
Which trisomy is associated with clenched hands and overlapping fingers?
Trisomy 18 (Edwards syndrome)
Which trisomy is associated with polydactyly?
Trisomy 13 (Patau syndrome)
