Prenatal Screening, Diagnosis, and Treatment

Question 1

What are the key characteristics of Cystic Fibrosis?

Answer 1

CD = AR disease with mutation in CFTR gene
Chronic lung disease and recurrent infection leading to lung scarring and cor pulmonale
85% have pancreatic insufficiency = chronic malabsorption and failure to thrive
Median survival about 40 years
delF508 and G542X are most common mutations
More common in caucasians

Question 2

Characteristics of sickle cell anemia?

Answer 2

AR
Point mutation in gene for beta-chain of hemoglobin
de-oxygenation causes sickling leading to hemolytic anemia, frequent pain crises due to vascular occlusion
More common among AA = all screened
Resistance to malaria
Maternal screen by hemoglobin electrophoresis which looks for HbS

Question 3

What is Tay-Sachs?

Answer 3

AR disease more common in ashkenazi jewish population
Founder effect
Deficiency of hexosaminidase A (hex A) which is degrades GM2 gangliosides
Accumulation of gangliosides in brain leads to enlarged neurons = neuronal death
symptoms of loss of alertness, excessive reaction to noise, developmental delay, neurological degeneration
Seizures
Cherry-red spot on fundoscopic exam
Paralysis, blindness, dementia, die by age 4

Question 4

How are thalassemias diagnosed?

Answer 4

CBC to look at Hgb and MCV (low)

Question 5

When are chromosomal abnormalities diagnosed?

Answer 5

Fetal karyotype
11-14 weeks - nuchal translucency, PAPP-A and beta-hCG
2nd trimester (15-18 weeks)= quad screen

Question 6

What is trisomy 21 also known as, and what are its characteristics?

Answer 6

Down Syndrome
Short stature, classic facies, developmental delay, mental retardation
Cardiac defects, duodenal atresia/stenosis, short limbs
Increased nuchal translucency, low AFP and estriol, high inhibin and b-hCG

Question 7

What is trisomy 18?

Answer 7

Edward syndrome
lethal, die within 2 years of life
clenched fists, overlapping digits, rocker bottom feet
VSD, TOF, omphalocele, congenital diaphragmatic hernia, NTD

Question 8

What is trisomy 13?

Answer 8

Patau syndrome

Holoporosencephaly, cleft lip and palate, cystic hygroma etc

Question 9

What is Turners syndrome?

Answer 9

45XO
Phenotypically female, short stature, low set ears, wide-set nipples, primary amenorrhea
Cystic hygroma can be sen on US*

Question 10

What are characteristics of klinefelters?

Answer 10

47XXX or XYUY
Small penis
infertility, gynecomastia
mental retardation

Question 11

When do NTD arise?

Answer 11

Week 4 of development

Question 12

What are NTDs due to?

Answer 12

Lack of folic acid

MTHFR mutations

Question 13

What are US findings of spina bifida?

Answer 13

Lemon sign and banana sign (cerebellum)

Question 14

What are lab tests associated with NTDs?

Answer 14

Elevated AFP

Question 15

What is Potter syndrome?

Answer 15

Renal failure leading to anhydramnios ( can be caused by potter’s disease which is bilateral renal agenesis)
Causes pulmonary hypoplasia, deformation of hands and limbs

Question 16

When is amniocentesis performed?

Answer 16

> 15 weeks
Needle transabdominally into uterus and amniotic sac
Can take 5-7 days to grow cells and perform FISH

Question 17

When is CVS performed?

Answer 17

between 9-12 weeks
Placing cathether into uterus (transab or transvag) and aspirating chorionic villi from placenta
higher risk of complication than amnio
Faster results because more cells taken

Question 18

What is percutaneous umbilical blood sampling?

Answer 18

phlebotomizing umbilical cord when fetal hct or platelet count needed in setting of Rh alloimmunization and fetal anemia
Can also be used to transfuse fetus