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Molecular and Cellular Princples of Medicine > Unit 7 - Birth Defects > Flashcards

Unit 7 - Birth Defects Flashcards

1
Q

what are the leading causes of infant mortality?

A

premature birth and birth defects

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2
Q

how many embryos spontaneously abort? how many are live-born with birth defects?

A

50% of embryos spontaneously abort

3-6% are born with birth defects

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3
Q

what are congenital malformations?

A

birth defects that are structural, behavioral, functional, or metabolic, and present at birth
-occur in 3% of live births (1:33), and account for 25% of deaths

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4
Q

per 1000 births, how many are:

  • NTD
  • cleft lip/palate
  • Down
  • cerebral palsy
  • heart defects
A 
<1 NTD
1 cleft
1.25 Down
3.1 cerebral palsy
5-10 CHDs (critical for life, very susceptible to errors)
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5
Q

what are the known causes of birth defects?

A
  • genetic problems (28%); Xm abnormalities or gene mutations
  • environmental factors (3-4%)
  • gene + environment (20-25%)
  • twinning (~1%); usually if conjoined
  • unknown (40-45%)
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6
Q

genetics of birth defects

A
  • can be due to single gene mutations
  • can be due to Xmal abnormalities
  • often sporadic
  • can be inherited as dominant, recessive, or X-linked
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7
Q

how many babies are born with defects caused by errors in number or structure of Xm? how do they come about?

A

1: 150

- inherited or de novo

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8
Q

what is Axenfield-Rieger syndrome? its symptoms?

A

a multi-system disorder that primarily affects eyes

  • hypertelorism (widely spaced eyes)
  • flattened mid-face with broad, nasal bridge
  • prominent forehead
  • microdontia or oligodontia
  • redundant periumbilical skin
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9
Q

what is the prevelence of Axenfield-Rieger syndrome? its inheritance? its cause?

A

1: 200,000 in autosomal dominant pattern
- caused by mutations in at least PITX2 and FOXC1
- -code for transcription factors in developing eye (anterior segment) and other body parts

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10
Q

what is the prevalence of holoproencephaly in embryos VS live-born infants? what are some causes?

A

1: 250 embryos, and 1:10,000 live-born
- caused by Xmal abnormality (25-50%); numerical trisomy 13, 18, and structural
- -18-25% are due to mutation in single gene
- environmental factors (maternal diabetes)

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11
Q

what is holoproencephaly?

A

structural anomaly of brain resulting from failed/incomplete forebrain division in 3rd and 4th weeks of gestation
-forebrain incompletely cleaves, causing defects in face and brain development

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12
Q

what are the most frequent deletions/duplications causing HPE?

A
  1. 13q
  2. del(18p)
  3. del(7)(q36)
  4. dup(3)(p24-pter)
  5. del(2)(p21)
  6. del(21)(q22.3)
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13
Q

what is the msot common environmental factor known to cause HPE?

A

maternal diabetes and recently statins

-alcohol and retinoic acid in animals

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14
Q

what are key genes implicated in HPE?

A

genes that operate on SHH (PTCH, GLI, DUSP)

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15
Q

what was the first linkage of infectious agents to birth defects?

A

rubella viral infections during pregnancy = congenital rubella syndrome

  • microcephaly
  • patent ductus arteriosus
  • cataracts
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16
Q

what effects do the following have on birth?

  1. Coxsackie B virus
  2. Toxoplasmosis
  3. hyperthermia
A
  1. increased spontaneous abortion
  2. cerebral calcifications and head defects
  3. disrupted neurulation and NTDs (from fever)
17
Q

birth defects associated with thalidomide and when

A

day 35-37: absence of ears and deafness
39-41: absence of arms
43-44: phocomelia with 3 fingers
46-48: thumbs with three joints

18
Q

what factors does susceptibility to teratogens depend on?

A
  1. genotype of embryo (gene-environmental factors) and mother (determine drug metabolism, resistance to infection, etc.)
  2. developmental stage at time of exposure (most sensitive period is weeks 3-8 during embryogenesis)
  3. dose and duration of exposure
19
Q

difference between fetal alcohol syndrome and fetal alcohol spectrum disorder

A

FASD refers to all alcohol-related defects (amount, timing, and genetics all contribute)
-FAS is most severe form on the spectrum

20
Q

what developmental problems can alcohol-affected fetuses have?

A
  • learning/remembering
  • understanding and following direcctions
  • controlling emotions
  • communicating and socializing
  • daily life skills (feeding, bathing)
21
Q

what is included in FASD?

A
  1. ARBD (alcohol-related birth defects)
  2. ARND (alcohol-related neurodevelopmental disorder)
  3. PFAS (parietal fetal alcohol syndrome)
  4. FAS (most severe)
22
Q

what structural defects are involved with FAS?

A
  • small head
  • epicanthal folds
  • flat midface
  • smooth philtrum
  • low nasal bridge
  • small eye openings
  • short nose
  • thin upper lip
  • dramatically smaller brain
23
Q

what are the proposed mechanisms of alcohol interference with embryo development?

A
  1. cell migration and adhesion
  2. cell proliferation and survival
  3. cell signaling and gene expression

cause exencephaly and nose/lip defects

24
Q

what is the most common birth defect?

A

malformation of the heart (1% of life briths, 10% of fetuses)

25
Q

what are the causes of congenital heart defects?

A

majority are multifactorial (gene-environment interactions)

  • 12% Xmal abmormality
  • 2% environmental teratogens
26
Q

what percentage of CHDs are atrial VS ventricular septal defects?

A

ASD: 10% of all CHD
VSD: 20% of all CHD (2-6 of every 1000 live births)

27
Q

what is dextrocardia? when does it cause problems?

A

heart is positioned on right side of thorax instead of left

  • caused by defects in establishing left-right body axis
  • if heterotaxy, can cause septal defects, double outlet right ventricle (DORV), and transposition of great arteries (TGA)
28
Q

what is DORV?

A

double outlet right ventricle

  • aorta arises from right ventricle, with pulmonary artery (left ventricle doesn’t provide anything)
  • always includes VSD to help infant
29
Q

what is TGA?

A

transposition of great arteries

  • main pulmonary artery and aorta are switched in position
  • often have septal defects to allow blood mixing
30
Q

what are signs and symptoms of severe heart defects in newborns?

A
  • rapid breathing
  • cyanosis
  • fatigue
  • poor blood circulation

many aren’t diagnosed until children are older

31
Q

22q11.2 deletion syndrome presentation

A

1: 4000 heterogenous multisystem syndrome
- 3 million bp deletion (30-40 genes)
- 5-10% of cases are inherited (AD)
- 80% have CHD
- -teratology of Fallot and truncus arteriosus
- palate defects
- mental retardation
- mild differences inf acial features

32
Q

what gives rise to the great arteries/

A

outflow tract of embryonic heart

33
Q

what happens in babies with truncus arteriosus?

A

aorta and pulmonary artery fail to separate completely, and usually associated with VSD

  • O2-poor and O-rich blood are mixed as blood flows to both lungs and rest of body
  • single common truncal valve controlling flow, and usually abnormal
  • -valve can be thickened and narrowed (blocks blood when it leaves) or leaky (goes back into heart)
34
Q

Tetralogy of Fallot problems

A
  1. VSD
  2. pulmonary stenosis
  3. overriding aorta (increases flow)
  4. ventricular hypertrophy
35
Q

how do cardiac neural crest cells contribute to outflow tract?

A

Tbx1 –> Fgf8 –> CNCC deployment

-these genes are located in the 22q11.2 deletion region

Molecular and Cellular Princples of Medicine (42 decks)

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