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Karyotypic Abnormalities Flashcards

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1
Q

How many cells does a karyotype typically analyze?

A

so it looks at living, dividing cells that are stopped in the middle of cell division

looks at chromo of 20 cells, deeply analyzing 5

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2
Q

What is the range for good band counts? poor band counts?

A

good = 550-650
poor = 350-450

(can dep on cell type, so like amniocytes will have weaker band count)

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3
Q

What ype of FISH can use cells that are not dividing?

A

Interphase FISH

(3-5 day turnaround time)

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4
Q

When is chromosomal disorder our first thought that comes to mind?

A

when you see a disorder that involved multiple unrelated systems + mult congenital anomalies

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5
Q

What is the suspected critical region os chr21?

A

21q21.22

but multiple regions are suspected; this is not quite known yet

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6
Q

What are 3 major anomalies in Tri21 taht we want to look for right away?

A
  • heart defect
  • duodenal atresia
  • Hirshsprung disease
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7
Q

What are some abnormal labs taht are associated with Tri21?

A
  • transient myelopoiesis (20-30% risk leukemia)
  • hypothyroidism
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8
Q

What are common cardiac findings in Tri21?

A

50% have heart anomalies:

40% AVSD
32% VSD
10% ASD
TOF 6%

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9
Q

Describe duodenal atresia and prevalence in Tri21

A

this is when the duodenum (C curve) has a blockage or discontinuity so that nothing can move through it –> baby cannot eat and stomach blows up w gas –> double bubble

25-40% kids w duo atresia have Tri21

5% kids w Tri21 have duo atresia

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10
Q

Describe Hirschsprung and its prevalence in Tri21

A

the ganglion cells (resp for squeezing + forward movement of stool) do not migrate to the rectum —> means absense of ganglion cells –> that area is small and v tight

leads to vomit + repeat –> baby needs surgical repair

this is V dangerous to send a child home w this

  • present in 2% Tri21
  • 12% w Hirsch have Tri21
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11
Q

What are some major physical findings in Tri21?

A

low tone (noticable right away)
microcephaly
brachycephaly
upslanting palpebral fissures
epicanthal folds
flat nasal bridge
tongue thrusting
small cupped ears
redundant nuchal skin
single palmar crease + clinodactyly 5th finger
sandal gap

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12
Q

What are some ENT + Vision problems we see in Tri21?

A

82% w frequent ear infections w conductive hearing loss (due to abnorm of eustachian tube bc absent nasal bone does not allow that pressure to equalize between the nose + the ear)

56% visual problems, usu near sighted

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13
Q

What are some autoimmune findings in Tri21?

A

risk of autoimmune disorders w thyroid + Celiac (bc have problems w absorption)

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14
Q

If patients w Tri21 are particularly active, what is something we want to look for?

A

they can have Atlanto-axial instability (base of skull to spine), so want to look at flexion and extension x-rays to make sure neck is ok

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15
Q

What is the avg age of development for Tri21?

A

2nd grader

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16
Q

Why is premature Alzheimer’s in adults common in Tri21?

A

the precursor protein in on Tri 21 (APP (amyloid precursor protein))

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17
Q

What are the fertility risks assoc w Tri21?

A

males = usu infertile
females = subfertile (15030% fertile)

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18
Q

What is risk for someone w Tri21 to have an affected child?

A

empirical data says 35-50%

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19
Q

What is approximate risk for woman age 40 to have child w Tri21?

A

1/100

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20
Q

What are the most common to least common causes for Tri21?

A

95% nondisjunction
- 90% maternal, 10% paternal
- 77% Mei I, 23% Mei II
- Mei I - usu maternal
- Mei II - usu paternal

4% Rob translocation
1% mosaicism
<1% partial dup

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21
Q

What are the recurrence risks of Tri21 w respect to the genetic cause?

A
  • Nondisjunction –> ~1-4% if <30y (then age related risk for >30y)
  • Rob trans –> empirically derived:
    — t(14:21) 10-15% maternal, <5% paternal
    —21q21a isochromosome: 100%
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22
Q

Causes of Tri18?

A
  • 94% maternal nondisjunction (usu Mei II) + association w mat age
  • 5% mosaicism
  • ~1% transloc or partial dup
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23
Q

What is the general prognosis for Tri18?

A

50% died w/in 1w birth

90% die by 1y (even w intervention) –> usu bc heart defect, primary apnea (stop breathing)

if they survive past 1y, then they are more likely to live longer

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24
Q

What are common physical findings in Tri18?

A

remember that everything is v small

  • char craniofacial features
  • overriding fingers
  • nail hypoplasia
  • short hallux
  • rocker bottom feet
  • short sternum
  • prominent occiput
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25
What % of babies w Tri18 die in labor?
38% also, 1/3 = premature
26
What is the most common major congenital anomaly we see in Tri18?
90% heart defects (VSD, mult valve anomalies)
27
What are major anomalies we see in Tri18 when thinking of Cardiac, Pulm, Opthalm, and ENT?
- heart defects - respiratory problems (laryngomalacia, trachoebronchomalacia, apnea, pulm HTN) - opthalmology (10% cataract, corneal opacities, photophobia) - ENT (mod-severe sensorineural hearing loss bc v small ears)
28
What are major anomalies we see in Tri18 when thinking of limbs, skeletal, renal, CNS?
- Limb anom (5-10%, radial aplasia, club foot) - Skeletal (scoliosis - more when older) - Renal (2/3 w horseshoe kidney, UTI more common) - CNS (5% brain anom; 25-50% seizures) Also - inc risk for neoplasia: Wilms tumor (1% risk), hepatoblastoma
29
What is the avg age for Tri18 developmentally?
older kids function at 6-8mo
30
What are some speech + motor skills that are lacking in Tri18?
most have no expressive language most cannot walk indep CAN recognize fam + smile at them older kids can maybe understand words, crawl, follow command, interact a bit w others
31
Can parents always opt for surgical intervention for Tri18?
- dep on institution - some will not provide surg intervention, some will for VSD for ex - want to respect parents wishes + also being realistic
32
Why do those w Tri18 need an abdominal US every 6 months?
- want to check for renal malformation + Wilms tumor + hepatoblastoma
33
3rd most common trisomy?
Tri13 (Patau syndrome)
34
What are 2 big features that you want to think about when thinking of Tri13?
holoprosencephaly cutis aplasia (think of that region on scalp that has no skin closure)
35
What are other main physical features of Tri13 other than holoprosencephaly + cutis aplasia?
- polydactyly - renal anomalies - eye anomalies (anophthalmia, microphthalmia)
36
What are som congenital anom assoc w Tri13?
CNS: holoprosencephaly, Dandy Walker (cerebellum) Heart: VSD, ASD, TOF, transposition of the great arteries GU: polycystic kidneys, uterine agenesis
37
What is the prognosis for Tri13?
- 50% die w/in 1month - 90% die w/in 1year (recent studies say maybe survival of 20%)
38
What are genetic causes of Tri13?
91% nondisjunction, usu Mei I
39
What are 3 prenatal indications for Turner syndrome?
hydrops, cystic hygroma, heart defect
40
What are some findings that might present in childhood/puberty to make the dx of Turner syndrome?
childhood - isolated short stature puberty - primary amenorrhea - lack of secondary sex char also, hypothyroidism
41
What are some birth anomalies associated with Turner syndrome?
- webbed neck - downslanting eyes - low set ears, posteriorly rotated - wide chest (w widely spacednipples) - puffy hands and feet (edema) - hyperconvex nails
42
What explains the short stature in Turner syndrome?
SHOX deficiency - can also see Madelung deformity (radius shortened w curvature of the arm) of note, can be responsive to growth hormone bc can overcome the signaling pathway
43
What explains the amenorrhea in Turner syndrome?
streak gonads --> since they are resp for providing estrogen for secondary sex devel subfertility to infertility = typical POF
44
Why might we see weight gain in Turner syndrome?
if they have hypothyroidism, then there may be poor metabolism in the muscles
45
What are common endocrine disorders associated with Turner syndrome?
95-100% w growth failure + red adult ht 90-95% w hypergonadotropic hypogonadism (gonads not resp well to the gonadotropins (FHS, LH) --> then they tell ovaries to release hormones, which cannot happen in this case) 15-50% glucose intolerance Type I diabetes 10% Type II diabetes
46
What are some main features of Klinefelter syndrome (47,XXY)?
hypergonadotropic hypogonadism (pituitary is great, then testes do not respond) male factor infertility tall stature low tone difficulties in school (w ELA) trouble regulating emotions
47
Why do those w Klinefelter syndrome (47,XXY) have tall stature?
they have an extra copy of SHOX
48
How are Klinefelter and Triple X simialr in presentation?
- speech dev delays - motor dev delays - mild reduction in IQ, usu more so bc of immaturity - tall stature - low tone
49
What trisomy had been historically ties to inc risk of imprisonment?
XYY Jacob's syndrome those were biased though, we know now that they usu have inc risk of autism, ADHD, emotional control
50
What causes Wolf-Hirschhorn?
4p- 55% w terminal del Ring 4 chromo 4p- mosaicism unbalanced transloc
51
What was a historical way to describe Wolf-Hirschhorn?
Greek warrior helmet facies
52
What are the most common findings in Wolf-Hirschhorn? (>75%)
- IUGR/postnatal growth def - ID - hypotonia - muscle hypertrophy (become small and skinny) - seizures - feeding difficulties - abnormal ears
53
What are the less common findings in Wolf-Hirschhorn? (<75%)
50-75%: - EEG abnorm - skeletal anom - craniofacial asymm - abnormal teething - ptosis - antibody def 25-50%: - heart defects - hearing defects - eye/optic nerve defects (like coloboma) - cleft/lip palate - structural brain anom - GU tract defects - renal anom
54
What causes cri du chat?
5p- 80-90% paternal in origin 10-15% due to unbal parental transloc 80-90% term del 3-5% bc interstitial del uncommon=mosaicism, inversions, ring chromo
55
What are the main findings associated with cri du chat?
laryngeal malformation resulting in high pitched monotone cry (hear meowing sound in nursery) dev delay/ID craniofacial findings other congen anom
56
What are some facial features associated with cri du chat?
- round face - prominent metopic bossing - broad nasal bridge, lateral downslanting palpebral fissures - hypertelorism - epicanthal folds - strabismus divergent/convergent - short philtrum - down turned corners of mouth - low-set ears of note, high arched palate is a big one dysm feat are not a dead giveaway for this one
57
What are some medical features associated with cri du chat?
35% congenital heart disease 30% abnormal MRI - absense corpus callosum - small cerebellum 18% renal abnorm - small kidneys, ectopic gential abnorm - cryptorchidism - inguinal hernia dev delay - mod to sev (dep on the del)
58
What is the cause of cat-eye syndrome?
isodicentric marker 22q11 --> tetrasomy q region gets dup around centromere
59
What are main findings in cat-eye syndrome?
- coloboma = "cat eye" (due to the defect in dev of the optic nerve) - preauricular anom (pits, tags) - hearing loss - heart defect - renal anom - anal atresia - ID (mild)
60
What are the causes of Turner syndrome?
40-50% = 45,X 15-25% = mosaicism 45,X/46,XX 20% = isochromosome ring X = present in a few women 10-12% women have some Y material (~3% present 45,X/46,XY)

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