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Stage 2: Human Deveopment > Congenital Abnormalities 2 > Flashcards

Congenital Abnormalities 2 Flashcards

1
Q

What is a syndrome caused by a translocation?

A

Sex-reversal syndrome

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2
Q

What are types of gene mutations that can result in a loss or gain of function?

A

1) Mutations in coding regions e.g. Apert’s syndrome (craniosynostosis), achondroplasia
2) Mutations in promoter/enhancer sequences e.g. Lieberberg syndrome, sex-reversal syndromes

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3
Q

What is hypohidrotic ectodermal dysplasia?

A
  • Genetic skin disease
  • Affects ectodermal organs e.g. hair, sweat glands, teeth (missing hair and not properly formed teeth, reduced ability to sweat due to no sweat glands )
  • In females the mammary gland is affected causing decreased milk production
  • The problems with sweat glands in the baby can lead to heat intolerance as they can’t regulate their temperature
  • Can’t go out in the day bc can’t thermoregulate
  • Mouse models - injection of Eda protein can reduce some aspects of syndrome
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4
Q

When are embryos most vulnerable to pathogens?

A

In the 1st trimester

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5
Q

What pathogens are embryos vulnerable to?

A

1) Toxoplasma parasite
2) Other viruses e.g. parvovirus
3) Rubella virus
4) CMV
5) HSV
6) HIV, syphilis, zika

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6
Q

What is the leading known preventable cause of mental and physical birth defects?

A

Alcohol

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7
Q

What are the clinical features of fetal alcohol syndrome?

A

1) Microcephaly
2) Short palpebral features (eye openings)
3) Epicanthal folds (folds over eyelids)
4) Low nasal bridge
5) Short nose
6) Flat mid face
7) Micrognathia (small jaw)
8) Thin upper lip
9) Smooth philtrum
10) Behavioural problems?

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8
Q

How many births are affected by fetal alcohol syndrome?

A

1 in 500 (50% of women of child bearing age consume alcohol) - binge drinking = 48g of alcohol (1 unit = 8g)

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9
Q

How does fetal alcohol syndrome arise?

A
  • Embryos can’t handle their drink as they have low fetal alcohol dehydrogenase activity
  • This cause molecular, epigenetic, metabolic and cellular changes
  • Brain is the last thing to develop
  • If mother drinks throughout pregnancy, this affects the CNS causing behavioural problems (also happens with IV drug users)
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10
Q

When do many of the fetal alcohol syndrome defects occur?

A

Within the first 6 weeks of pregnancy

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11
Q

Why do neural tube defects develop?

A

Severe congenital malformations resulting from lack of/incomplete neural tube closure

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12
Q

What is spina bifida occulta?

A
  • “Closed” spina bifida
  • Malformation of one or more vertebrae
  • In most cases, it causes no problems
  • Neural tube is ok just defect around it e.g. tethered spinal cord (v important to spot via MRI)
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13
Q

What are the neurocutaneous signatures of spina bifida occulta?

A
  • Pigmented nevus (mole)
  • Hairy tuft
  • Angioma
  • Lipoma
  • Dimple
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14
Q

What is myelomeningocele?

A
  • The most severe type of spina bifida
  • The baby’s spinal canal remains open along several vertebrae in the back, allowing the spinal cord and protective membranes around it to push out and form a sac in the baby’s back
  • Protruding meninges and spinal cord
  • Defect at and below lesions
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15
Q

What are the clinical features of myelomeningocele?

A
  • Open lesions - bloody, undeveloped
  • Lack of sensation
  • Incontinence
  • Unable to walk
  • 10% babies die in first year
  • In utero surgery required
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16
Q

What defects is myelomeningocele linked to?

A

1) Hydrocephaly (build up of CSF compresses the brain)

2) Gut and genital tract defects

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17
Q

What is spina bifida and what causes it?

A
  • Incomplete closure of the spinal cord (split spine)
  • Caudal neuropore doesn’t close
  • Caused by defects in early neural development
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18
Q

How is spina bifida identified?

A

Fetal abnormality US

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19
Q

What is a complication of spina bifida?

A

Arnold-Chiari malformation

  • The cerebellum extends into the foramen magnum
  • The back of the brain is forced down through the skull into the top of the spinal canal
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20
Q

How is fetal surgery done to treat spina bifida?

A
  • Fetal surgery to close the neural tube before 26 weeks can reduce the severity of the defect in some cases and prevent Arnold-Chiari malformation
  • Centre in UCL to do this surgery
  • Otherwise surgery is carried out after birth
  • Problem - mother’s are pressurised to have surgery when they may not want to have it
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21
Q

Why does fetal surgery for spina bifida have to be done before 26 weeks?

A
  • Toxic substances e.g. urine in the amniotic sac would cause the neural tube to degenerate
  • Once it has degenerated it can’t be repaired
  • Therefore the neurons would degenerate if exposed to amniotic fluid beyond 26 weeks
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22
Q

What vitamin is preventative of NTDs?

A

Folic acid

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23
Q

What does folic acid do?

A
  • It is required for the synthesis of DNA bases esp. thymine and therefore DNA replication and cell division
  • Also required for amino acid metabolism and a number of single-carbon-transfer reactions
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24
Q

How does folic acid affect NTDs?

A
  • Folate deficiency predisposes susceptible people

- Therefore taking folate before pregnancy decreases the risk for some individuals

25
Q

What is the recommended intake of folic acid to prevent NTDs?

A
  • Women should take a daily dietary supplement of 0.4mg of folic acid when trying to conceive
  • This may reduce NTD by as much as 70%
26
Q

What medication is contraindicated in pregnancy?

A

Valproic acid (Sodium valproate)

27
Q

What is valproic acid used to treat?

A
  • Manic episodes associated with bipolar disorder
  • Migraine prophylaxis
  • Epilepsy
28
Q

Why is valproic acid contraindicated in pregnancy?

A
  • Valproic acid slows the closing of the neural tube, so increases the risks of it not closing at all
  • It can cause ‘minor malformations’ e.g. small fingers and toes or ‘major malformations’ e.g. spina bifida or a cleft palate
29
Q

What are problems in mesodermal development linked to?

A

Skeletal and limb patterning defects

30
Q

When is the embryo most susceptible to teratogens/teratogenesis and infectious agents?

A

During the embryonic period (3-8 weeks, peak at 5 weeks) when most organs are developing

31
Q

What are two examples of skeletal defects?

A

1) Spondylocostal dysostosis - defect in formation of somites (paraxial mesoderm)
2) Achondroplasia - defect in development of cartilage (mesoderm)

32
Q

What is used to make different digits?

A

Sonic hedgehog, morphogen gradient, zone of polarising activity (ZPA)

33
Q

What does gain of Shh anteriorly lead to?

A

Digit duplication (two sets of toes on one foot)

34
Q

What is Liebenberg syndrome?

A

Arm to leg transformation (arm looks like leg due to Pitx1 being expressed in the developing arm as well)

35
Q

How does Liebenberg syndrome happen?

A

1) In normal development, expression of the transcription factor, Pitx1 instructs the developing limb to form a leg
2) In contrast, another transcription factor, Tbx5, instructs the developing limb to become an arm
3) In these families, the transcription factor Pitx1 is expressed in both the developing arm and leg - this is due to a mutation in the promotor sequence that determines where Pitx1 is expressed
4) In this example, the mutation has resulted in Pitx1 being expressed in the wrong location (in the developing arm) in addition to its normal expression the developing leg

36
Q

What are four endodermal defects?

A

1) Lung aplasia - missing lung
2) Oesophageal atresia/fistula - problem with the division of trachea and oesophagus so baby feeds can go into the lung (can see on US)
3) Omphalocoele - gut outside body cavity, often associated with T13
4) Gastroschisis - intestines outside body, abdominal wall does not form completely
5) Midgut hernia
6) Atresia and malformation defects

37
Q

Is the liver big or small in the fetus and why?

A

The liver is very large in the fetus bc it makes most of the blood before the bone marrow develops

38
Q

What are do neural crest cells (multipotent cells) give rise to?

A

PNS, part of the heart and most of the face

39
Q

What should you think if you see a facial defect?

A

That maybe the baby has an underlying neural crest related heart defect

40
Q

What are 5 examples of defects in neural crest cell development (neural crest disorders)?

A

1) Bilateral cleft lip
2) Pierre-Robin sequence - underdevelopment of lower jaw
3) Hirschsprung’s disease
4) Neurofibromatosis - nasty child tumour
5) Neuroblastoma

41
Q

How does Hirschsprung’s disease develop?

A
  • Caused by failure of the vagal neural crest to migrate into posterior regions of the gut - nerves in gut don’t form properly
  • As a consequence, the bowel’s contents build up proximal to the affected region, causing it to expand
  • Part of the gut (colon) is not undergoing peristalsis bc it has no enteric nervous system
42
Q

When do most birth defects arise?

A

Between 3-8 weeks of embryonic development

43
Q

What are the pre-natal risk factors for brain development?

A

1) Maternal health
2) TORCH - exposure to specific set of viruses esp. congenital rubella, measles and its complications in childhood, AIDS
3) Maternal substance misuse
4) Maternal age e.g prematurity in teenage mothers or older mother births
5) Maternal mental health
6) Environmental toxins

44
Q

What are the post-natal risk factors for brain development?

A

1) Birth complications
2) CNS infections e.g. sepsis, meningitis
3) Nutrition
4) Socio-emotional
5) Environmental toxins incl. lead exposure

45
Q

What defect can occur at the induction (dorsal) phase of brain development in weeks 3-4 and describe its features?

A

Myelomeningocele (spina bifida)

  • Failure of closure of the spinal cord
  • Arises from genetic or nutritional problems
  • Results in motor and perceptual deficits
46
Q

What defect can occur at the induction (ventral) phase of brain development in weeks 5-6 and describe its features?

A

Holoprosencephaly

  • Failure to form two hemispheres of the brain
  • Failure of forebrain to divide and develop
  • Associated with other midline and facial defects, trisomy 13
  • Often genetic origin
  • Severity varies from not being compatible with life to more mild mental retardation
  • Usually incompatible with life
47
Q

What defect can occur at the proliferation phase of brain development in months 2-5 and describe its features?

A

Microencephaly

  • Early cessation of cell division
  • Abnormally small head
  • Genetic or trauma factors e.g. infection, fetal alcohol syndrome, valproate
  • Associated with low intellectual abilities/learning disabilities
48
Q

What are causes of atypical development (developmental differences can be caused by influences occurring at several time points in a child’s life)?

A

1) Antenatal exposure - teratogens, maternal drug and alcohol abuse
2) Poor maternal health
3) Child abuse/neglect
4) Genetic factors
5) Nutrition
6) Perinatal complications - prematurity, birth complications, neonatal illness (sepsis/stroke)
7) Infections
8) Unknown
9) Paternal health - need to also ask about parent who isn’t there

49
Q

Describe features of the new born

A
  • All nerve cells are present but in an undeveloped state
  • Growth and development occurs in an experience dependent way
  • Perceptual/motor development - initially limited repertoire but rapid and orderly development
50
Q

What is amblyopia?

A
  • When the anatomy of eye is normal but squint is present because of problem with eye muscles
  • Information from that eye doesn’t get to the visual cortex so the visual nerve pathway can’t develop
  • The brain uses information from the good eye and discards information from the lazy eye
  • If it is picked up too late it will not make a difference so there is a critical period - same for hearing impairment, want to put cochlear impact in early
51
Q

What does ACE mean in child development?

A

Adverse childhood experiences

52
Q

What is anencephaly?

A
  • Incomplete closure of the upper end of the neural tube (no brain)
  • Brain dissolves in amniotic fluid, cranial neuropore doesn’t close
53
Q

How does the CNS develop?

A

Neural fold to neural tube (at 21-28 days) to spinal cord and brain

54
Q

What is a sacrococcygeal teratoma?

A
  • Remnant of primitive streak
  • All 3 cell line derivatives in one tumour, contains tissue from all 3 germ layers
  • Can take such a big blood supply from the fetus that it can cause fetal heart failure
  • Massive bulge/tumour on baby’s/fetus’ body
55
Q

What are neural tube defects?

A

1) Spina bifida

2) Anencephaly

56
Q

What is the most common problem causing congenital heart defects?

A

Formation of chambers

57
Q

What do we need to do to reduce the number of teratogenic pregnancies?

A
  • Need to reduce the number of drugs given to women in early pregnancies unless know to be safe for a long time e.g.. not aspirin?
  • No register of IVF pregnancies and what they are taking around conception
58
Q

What is DES (diethylstilbestrol)?

A
  • Synthetic oestrogen given in the first trimester for anti-emetic
  • Female offspring developed very early cervical and vaginal cancers in teens and early 20s

Stage 2: Human Deveopment (34 decks)

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