Birth Defects - RR

Question 1

List in order of increasing prevalence the incidence of birth defects: Downs, cerebral palsy, neural tube defects, congenital heart defect, cleft lip

Answer 1

Neural tube defects< cleft lip < Down’s < Cerebral palsy < congenital heart defect

Question 2

What are different causes of birth defects (there are 4 large categories)?

Answer 2

1. Due to a single gene mutation
2. due to a chromosomal abnormality
3. Sporadic (happened during meiosis)
4. Inherited

Question 3

What is Axenfeld Rieger syndrome? What is mutated?

Answer 3

This is a disease where a single gene mutation causes a variety of defects including occular defects, widely spaced eyes, dental abnormalities, periumbilical folds, and craniofacial issues
Caused by mutations in PITX2 and FOXC (both are transcription factors)

Question 4

Two patients with that same mutation have different phenotypes. What causes this phenomenon?

Answer 4

The environment plays a role- where the embryo develops and what it’s exposed to. These mutations might not be deleterious on their own, but in combination with environmental factors may see the clinical phenotype

Question 5

What are different causes of holoprosencephaly?

Answer 5

Chromosomal abnormalities, environmental conditions (for example mom had diabetes), single gene mutations

Question 6

What genes have been indicated in holoprosencephaly?

Answer 6

SHH (sonic hedgehog) is major

Also PTCH1, GLI1, and DISP1

Question 7

What are the birth defects associated when a pregnant woman contracts German measles (viral rubella)?

Answer 7

Cataracts, heart defects, and microcephaly

Question 8

What are some infectious agents that when a pregnant woman contracts causes birth defects?

Answer 8

Coxsackie virus, cytomegalovirus, herpes, parvo virus, syphilis, rubella

Question 9

How does a pregnant woman getting hyperthermia (fever) affect development?

Answer 9

Can result in neural tube defects if occurring during this stage of development

Question 10

What is an example of a pharmacologic agent that can cross the placenta and cause birth defects? What are the defects?

Answer 10

Thalidomide

If taken at 35-37 week then ears absent or deaf, if taken at 43-44 week then born with phocomelia (no arms)

Question 11

Define tetralogy and teratogen

Answer 11

Tetralogy- the study of birth defects

Teratogen- agents that cause birth defects

Question 12

What are factors that determine if the embryo/fetus will be susceptible to a teratogen?

Answer 12

1. Developmental stage at the time of the exposure
2. The dose and duration of exposure
3. Genotype of embryo (or mom)- for example how you metabolize a drug

Question 13

What is the most sensitive time for inducing birth defects?

Answer 13

3-8 weeks (the embryonic period)

Question 14

What happens if there’s a malformation during the first two weeks of development?

Answer 14

The embryo isn’t viable and will die

Question 15

What is the difference between fetal alcohol syndrome and fetal alcohol spectrum disorder?

Answer 15

Fetal alcohol syndrome is the most severe form of fetal alcohol spectrum disorder, which is the overarching category

Question 16

What are the characteristics of fetal alcohol syndrome?

Answer 16

Small head, small eyes, short nose, smooth philtrum, underdeveloped jaw, mental retardation/developmental issues