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Genetics Final > Case #5 Translocational Down Syndrome > Flashcards

Case #5 Translocational Down Syndrome Flashcards

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1
Q

Patient’s mother’s History

A

Shawana Ubo mother, 23 years old

Bbay girl that was 2500 grams, 30 week gestation

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2
Q

Baby Hx

A

decreased muscle tone
low birith weight
protential for developing respiratory issues b/c baby is not full term

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3
Q

Facial features

A

nasal root, flattened maxillary and malar region

produces characteristic appearance fo trisomy 21

Facial profile is flater than normal (middle and right image)
Hands and feet are short and rounded and may have a palmar (plantar) crease.

Hypotonia is present

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4
Q

Floppy Infant Syndrome (FIS)

A

consider it as a potential Dx

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5
Q

What diseases have infant hypotonia as a symtpom (8)

A
  1. Krabbe disease
  2. Prader-Willi Syndrome
  3. Aicardi syndrome
  4. Myasthenia gravis,
  5. Kernicterus
  6. Muscular Dystrophy
    7, Rett’s Syndrome
  7. Spinal muscular atorphy
  8. Marfan’s syndrome
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6
Q

Krabbe syndrome

A

CNS disorder;
globoid cell leukodystorphy
autosomal recessive

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7
Q

Prader-Willi syndrome

A

Chromosome 15q deletion

exhibits genetic imprinting (differnt phenotype with paternal versus maternal inheritance)

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8
Q

Aicardi syndrome

A

X-chromosome mutation

ass with absence of corpus callosum

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9
Q

Myasthania Gravis

A

autoimmunie disease of NMJ

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10
Q

Kernicterus

A

Bilirubin-induced brain dysfunction

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11
Q

Muscular Dystrophy

A

X-linked damage to skeletal muscle

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12
Q

Rett’s syndrome

A

Nuerodevelopmental disorder ass. with microencephaly, small hands and feet

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13
Q

Marfan’s Syndrome

A

autosomal dominant mutation in CT with mutaiton in FBN1 which assocaites with tumor necrosis factors B-1 (TNF-Beta)

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14
Q

Spinal Muscular Atrophy

A

Collection of genetic muscle mutations both autosoal and sex-liinked
most of thema re recessive in inheritance pattern

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15
Q

Baby Barika’s symptoms

A

dysmorphic features including upslanting palpebral fissures, epicanthal folds, poor moro reflex

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16
Q

What was Barika’s cardiac exam

A

prouces holocystolic murmur

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17
Q

What were Barika’s hands lke

A

short with wtout and stubby fingers

Prominant palmar crease

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18
Q

What are signs and symptoms caused by FAS (5)

A
  1. low birth weight
  2. small head circumference
  3. fialture to thrive
  4. organ dysfunction
  5. facial abnormalities, inclduing smaller eye openings, flattened cheekbones, and indistinct philtrum (underdeveleoped groove between ose and upper lip)
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19
Q

B/c of FAS, as child maturees, may exihibit

A

epilepsy
developmental delay
poor coordination/fine otor skills
poor socialization skills, such as difficulty buidlign and maintinta freinsdhips and relatting to groups

lak of imagination or curiosity

learnng difficulties including poor memeroy, inability to understand concepts sucha s time and money, poor language comprehension, poor problem-solicng skills

behavior prolbems including hyperactiivyt, inabiltiy to concentrate, scial withdrawal, subborness, impulsiveness, asnxiety

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20
Q

What is moro relex-

A

remove body weight of baby from pad, rleease head and allow it to fall back again, normal response is for baby to have startled look, arms shoudl move sideways with palms upa nd thumbs flexed, may cry for a minute, as reflex ends,infatn draws its arms back to body with elbows flexed, then rlexases

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21
Q

Absence moro reflex on both sides uggest

A

damage to brain or spinal cord

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22
Q

Absene on only one side

A

suggests ether broken clavicle or injruty to brachial plexus

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23
Q

What is a holosystolic murmur

A

murmur heard throughout all of systole and can be ass. with a mitral valve or tricupside valve regurgition or ventricular-septal defect

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24
Q

what is a TTE

A

transthoracic echocardiography (TTE) is a protable and noninvasive and provides rapid sonogram of heart

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25
Q

What is the clinical trial called?

A

Biology Study of Transient Myeloproliferative Disorder (TMD) in cChildren with Down Syndrome

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26
Q

What is the rationale of clinical trial

A

Studying the genes expressed in sampels of blood from patients with DS may help doctors ID biomarkers related to cancer

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27
Q

Purpose of clinical trial

A

to looka t blood samples from newborns with DS.

Necessary to est database of ino of inants iwth gentic disorder only, cancer only, and comorbi presentation of both diseases

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28
Q

How long does genetic testing last

A

a couple days to proecss

29
Q

What is incidence of Tirsomy 21

A

Most common autosomal disorder-

1/700-1000 live births

30
Q

What is the majority of cases of DS caused by

A

nondisjuntion

47, XX, +21
47, XY, +21

31
Q

Who was the disorder named after

A

John Langdon Down

32
Q

when dd he discoer it

A

describedd cohort of children with mental retardation that had very similar morphological characteristics in 186

first named them mongoloids

33
Q

WHen does trisomy 21 occur (translocation)

A

error or nondisjunction occurs in teh egg or sperm cell that becomes the zygote and leads to TRISOMY 21,

error is at very beginning of development, every cel that comes from this zygote will hvae an extra chromosome 21

34
Q

what is Robertsonian Translocation?

A

rare cause of DS,
unbalanced
occurs beween two ACROCENTRIC chromosomes and fusion of two long arms of each chromosome occurs with loss of short arms (not deleterious)

35
Q

What kind of “muaiton” did Shawana have?

A

Balanced translocation

most common between 14 and 21

36
Q

How did Barika get DS

A

Mom’s 14,21 + normal 21 from EACH parent (2 21s), then chidl will have DS

37
Q

What is inheritance pattern>

Chance inheriting 14,21 translocation?

Chance of developing DS

A

Offspring has 50% chance of inheriting 14.21 translocatino from affected parent

25% chacne offpsring ris for developing DS

38
Q

Can children be phenoyptially norma?

A

if mother passes along her nomral 14

if mother passes her 14,21 without passing along an additioanl chromosome 21

39
Q

What is the mutated gene refereed to

A

14q21q (two q arms)

40
Q

what is MOSAIC type of DS

A

nondisjucntion of 21 occurs very early in MITOTIC division AFTER FERTILIZATION so only one of the two cell lines shows a trisomy for Chromsoome 21

Therefore, peopel with DS have 2 cell lines- one with normal nmber chromosomes, and one iwth extra #21

41
Q

How is Mosaic DS Dx?

A

detected by blood test at birth or during AMNIOCENTESIS or CVS duing pregnancy

Typically chromosomes in 20 different cells are counted

If 2+ / 20 cells are normal (have 46 chromosomes) and others have extra #21 (total of 47 chrosomeoms) , bab is said to have mosaic DS

42
Q

What happens if mosiacism is supected

A

Cytogenetiist ( chromosome specialist) will suualy count extra cells to confirm Dx

43
Q

What is a cytogenetecisst

A

chromosome specialist

44
Q

How is Mosaicism described? What if there are a total of 50 cells. 10 cells are normal cell lines and 40 have extra number 21 chorosomes

A

The level of mosaisicm is said to be 80%

or 40/50 !

45
Q

How accurate is percentage mosaism. Are biopsies usually done

A

while % is usually determiend by blood cells, % may be different in other tissues or parts of the body! (i.e. 80% can actually have full trisomy in skin or brian cell)

Biopsies are not usually done b/c theya re invasive and usually dont give any inof bout how a eprson with mosaic DS will ultimately funciton

46
Q

what is the GENE-DOSAGE EFFECT of Trisomy 21 mechanims

A

DS pehonotype is caused by increased expression of specific genes

47
Q

What does extra copy f proximal part of 21q.22.3 lead to

A

gives rise to phenotype of DS including mental retardation, facial features, hand anomalies, and cardiac defects

48
Q

What is the “DS Critical Region”

A

theory that only a small protion of the chrosoome actually needed to be triplicated to get effects seen in DS

not a small isolated spot, but likely several ares that are not necesarly side by side

49
Q

HOw many genes does Chrosome 21 have

A

200-250 genes

salles chrosome in teh body in ter so number of genes

50
Q

GEnes that may contribute to variable pheontype in DS include

A 
Superoxide Dismutase (SOD1)
COL6A1
ETS2
CAF1A
Cytathione BEta Synthase (CBS)
DYRK
CRYA1
GART
IFNAR

APP, GLUR5, S100B, TAM, PFKL

51
Q

Has any gene been fully linked to any feature ass iwth DS>

A

NO!

52
Q

SOD1

A

overexpresion may cause premature again and dec fucntion of immune system
role in Senile Dementia of Alzheimers type or decresed cogntion is sitll speculative

53
Q

COL6A1

A

over expression may be the cause of heart defect

54
Q

ETS2

A

over expression may be the cause of Sk abnormalities

55
Q

CAF1a

A

overexpression may be detrimental to DNA synthesis

56
Q

CBS (Cystathione Beta Synthase)

A

overexpression may disrupt metabolism and DNA repair

57
Q

DYRK

A

overexpression may be cause of mental retardation

58
Q

CRYA1

A

over expression may be cause of cataracts

59
Q

GART

A

overexpression may be cause of cataracts

60
Q

IFNAR

A

gene of expression of Interferon, over expressio may interefire with immune system as well as other organ ystems

61
Q

what are most common cardiac defects

A

Endocardial Cushion defect
ventricular septal defect
tetralogy of allot

62
Q

GI defects ass with DS

A

duodenal atresai (closure or absenec)
annular pancreas
Hirschpung disease

63
Q

Long term consequence of DS

A

higher risk of leukemia, hypothyroiism, cervical spine instability

64
Q

What IQ do they have?

A

20-35, severe
35-50 moderate
50-70 mild

65
Q

Is there a cure of DS

A

no

AAP.org- american acadamey of pediatrics

66
Q

How to manage if hchld has it

A

screen children for cardiac defects
GI defects
Hearing and vision loss
hypothyroidsim

67
Q

What kind of prenatal screenign can be done?

A

1st trimester with combo of fetal ultrasound to meausre nuchal translucency

Blood tests to measure levels of pregnancy-ass. plams protein A (PAPP-A)

HCG

68
Q

What kind of creenign can be done at 15-20 week gestation

A

quad screenign consisting of alpha fetal protein,
estriol
HCG
inhibin A

amniocentesis of CVS can be performed to acheive a definitieve diagnosis

69
Q

Social implications of having DS or being a caregiver

A

yep

Genetics Final (8 decks)

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