PATH - Autosomal trisomies

Question 1

Down syndrome

Answer 1

trisomy 21

Findings: intellectual disability, flat facies, prominent epicanthal folds, single palmar crease, gap between 1st 2 toes, duodenal atresia, Hirschsprung disease, congenital heart disease (eg, atrioventricular septal defect), Brushfield spots.

*First-trimester ultrasound :
INC nuchal translucency and hypoplastic nasal
bone
INC free β-hCG
DEC serum PAPP-A

*Second-trimester quad screen:
INC β-hCG
INC inhibin A
DEC α-fetoprotein
DEC estriol

Associated with early-onset Alzheimer disease (chromosome 21 codes for
amyloid precursor protein) and INC risk of ALL
and AML.

95% of cases due to *meiotic nondisjunction
(INC with advanced maternal age)

Question 2

Edwards syndrome

Answer 2

trisomy 18

Election age (18)

Findings: severe intellectual disability, rocker bottom feet, micrognathia (small jaw), low-set Ears, clenched hands with overlapping fingers, prominent occiput, congenital heart disease.

*first trimester screen:
DEC PAPP-A
DEC free β-hCG

*Quad screen:
DEC α-fetoprotein
DEC β-hCG
DEC estriol
DEC or normal inhibin A.

Death usually occurs within 1 year of birth.

Question 3

Patau syndrome

Answer 3

trisomy 13

Puberty (13)

Findings: severe intellectual disability, rockerbottom
feet, microphthalmia, microcephaly, cleft liP/Palate, holoProsencephaly,
Polydactyly, congenital heart disease, cutis aplasia

First-trimester pregnancy screen:
free
DEC β-hCG
DEC PAPP-A

Death usually occurs within 1 year of birth.