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Cardiovascular Block: Week 7 > Sex Chromosome Abnormalities and Microdeletions (Chromosome Disorders 2) > Flashcards

Sex Chromosome Abnormalities and Microdeletions (Chromosome Disorders 2) Flashcards

1
Q

Do autosomal aneuploidies or X/Y aneuploidies produce a more severe phenotype?

A

Autosomal aneuploidies (sex chromosome aneuploidies less severe due to X inactivation)

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2
Q

What is the prevalence of sex chromosome abnormalities?

A

Aneuploidy of X or Y is estimated to occur in 1/500 live births - COMMON (also a very common cause of miscarriage)

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3
Q

What do sex chromosome aneuploidies result from?

A

Meiotic non-disjunction

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4
Q

What is the prevalence of Klinefelter Syndrome?

A

1/600 - 1/800 male live births; 3.1% of infertile males

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5
Q

What is the primary karyotype in Klinefelter Syndrome?

A

47, XXY

80% of cases

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6
Q

What are other karyotypes in Klinefelter Syndrome?

A

48, XXXY; 49, XXXXY; Mosaic 46,XY / 47, XXY

20% of cases

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7
Q

What are the majority of Klinefelter Syndrome cases due to?

A

Maternal meiotic non-disjunction in 56%, rest due to paternal non-disjunction (majority occur during maternal meiosis)

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8
Q

What are the clinical features (physical) of Klinefelter Syndrome during the pre-pubertal period?

A

Mild, often normal

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9
Q

What are the clinical features (physical) of Klinefelter Syndrome during puberty?

A
  • Height average to tall (long legs)
  • Gynecomastia (50%)
  • Small, firm testes (orchidometer)
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10
Q

What are the clinical features (physical) of Klinefelter Syndrome during adulthood?

A
  • Infertility (all)
  • Decreased libido (70%)
  • Decreased beard growth
  • Osteoporosis
  • Muscle weakness
  • Thromboembolic disease
  • Obesity
  • Diabetes
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11
Q

What are the cognitive clinical features of Klinefelter syndrome?

A
  • IQ: decreased 10-15 points (when compared to other family members)
  • Specific areas of difficulty: language, executive functions
  • Nearly all have medical, social or psychological problems
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12
Q

What social / psychological problems are often seen in Klinefelter syndrome?

A

They tend to be introverted, shy, awkward, and often feel more comfortable with kids younger than themselves than kids of their own age.
(testosterone replacement can help with this)

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13
Q

What are some of the complications of Klinefelter syndrome?

A
  • Cardiovascular disease / respiratory disease

- Low testosterone levels, other endocrine abnormalities (including DM)

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14
Q

When is the diagnosis of Klinefelter syndrome usually made?

A

Usually during adolescence or as an adult (26%); with 10% prenatally (very difficult to provide prenatal counseling)
BUT
The majority of patients remain undiagnosed (64%)

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15
Q

How is diagnosis of Klinefelter syndrome made?

A

Can be detected on PCR aneuploidy screen

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16
Q

What are the 4 main areas of care and management fro Klinefelter Syndrome patients?

A
  1. Testosterone replacement
  2. Infertility
  3. Cognitive issues
  4. Cosmetic issues
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17
Q

In the management for Klinefelter Syndrome, what is the importance of testosterone replacement?

A
  • Increases masculinity, strength, libido, bone density, body hair, benefits CVS
  • Decreases fatigue and irritability
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18
Q

In the management for Klinefelter Syndrome, what can be recommended as options for infertility?

A
  • ICSI (in vitro technique) as a reproductive option

- BUT there is an increased rate of disomy gametes (not always successful)

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19
Q

In the management for Klinefelter Syndrome, how should the management of cognitive issues be approached?

A
  • Developmental assessment
  • OT/PT/ST if required
  • Psychology assessment
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20
Q

In the management for Klinefelter Syndrome, what cosmetic issue can be addressed?

A

Surgery for gynecomastia

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21
Q

What is the prevalence of Turner Syndrome?

A

1 / 2500-3000 live female births

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22
Q

What is the primary cause of Turner Syndrome?

A

75% due to loss of paternal sex chromosome

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23
Q

What is the most common karyotype in Turner Syndrome?

A

45, X (50% of cases)

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24
Q

Apart from the most common karyotype, what other Turner Syndrome karyotypes are seen?

A
  1. Mosaicism e.g. 45, X / 46, XX (20% of cases)
  2. Isochromosome 46, X, i(Xq) (15% of cases)
  3. Other, including ring X (46, X, r(X) ) and deletion Xp (15% of cases)
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25
Q

What are the prenatal physical features of Turner Syndrome?

A
  • Increased nuchal translucency / edema
  • Abnormal triple screen
  • Usually an incidental finding = implications for genetic counseling
26
Q

What are the neonatal physical features of Turner syndrome?

A
  • Puffy dorsum hands and feet
  • Nuchal skin fold / webbed neck
  • Cardiac abnormalities (typical coarctation of the aorta but they get others too)
27
Q

What is the severity of Turner Syndrome vs. Klinefelter Syndrome?

A

Turner syndrome = more severe findings and implications than Klinefelter syndrome

28
Q

What are the postnatal clinical features of Turner Syndrome?

A
  1. Short stature (average about 145cm)
  2. CVS abnormalities (17-45%)
  3. Renal abnormalities
  4. Skeletal abnormalities
  5. Delayed puberty, amenorrhoea, INFERTILITY
  6. Endocrine complications
  7. Deafness (44-90%), recurrent otitis media
  8. Squint, cataracts, nystagmus
29
Q

What CVS abnormalities are seen in Turner Syndrome?

A
  • Coarctation of the aorta, bicuspid AV, VSD

- Hypertension, conduction defects

30
Q

What is the life expectancy of Turner Syndrome patients?

A

~25 years (27.9 years)

31
Q

What is the most likely cause of the decreased life expectancy seen in Turner Syndrome patients?

A

The CVS abnormalities seen in 17-45% of patients.

32
Q

What skeletal abnormalities are seen in Turner Syndrome?

A

Increased carrying angle (elbow), CDH, scoliosis

33
Q

What endocrine complications are seen in Turner syndrome?

A

Obesity, hypothyroidism

34
Q

What is the prevalence of cognitive abnormality in Turner Syndrome patients?

A

10% significantly delayed (all karyotypes)

  • 70% will have visuo-spatial problems
  • Problems with maths, driving and social function
35
Q

Mental retardation in Turner Syndrome is most common with which karyotype?

A

Ring X Chromosome

36
Q

What is diagnostic of Turner Syndrome?

A

Absence of all or part of a second sex chromosome

37
Q

What can be used to diagnose Turner syndrome? And which test is the gold standard?

A
  1. Karyotype (gold standard)

2. PCR aneuploidy

38
Q

How is diagnosis of Turner Syndrome on karyotype made?

A
  • Usually okay to analyze 20 cells
  • If strong suspicion & normal karyotype, count 100 cells
  • DNA testing for Y material only if masculinized or unidentified marker chromosome (FISH)
39
Q

What should be done for the care and management of patients with Turner Syndrome at diagnosis?

A
  • BP check
  • Echo
  • Renal U/S
  • TFT
  • Hearing screen
  • Remove gonads if Y material (at risk for malignancy)
40
Q

What should be done for the care and management of patients with Turner Syndrome during childhood?

A
  • Check growth
  • BP
  • Psychosocial issues
  • GH therapy
  • Sex hormones
41
Q

What should be done for the care and management of patients with Turner Syndrome during adulthood?

A
  • BP
  • TFT
  • Hormone therapy
  • mx of infertility: Spontaneous pregnancies in mosaics, increased risk of miscarriage, twins, aneuploidy - option of donor eggs (if normal structure to uterus)
42
Q

What are microdeletion syndromes?

A

Microdeletions involve loss of a few genes at closely adjacent loci or loss of many loci
= clinically recognizable phenotype

43
Q

How are microdeletion syndromes diagnosed?

A 
Usually submicroscopic (not visible on standard karyotype) 
Diagnosis: 
- FISH 
- Array-CGH 
- MLPA
44
Q

Which chromosome is involved in Cri du Chat Syndrome?

A

5p

45
Q

Which chromosome is involved in 1p36 Deletion Syndrome?

A

1p

46
Q

Which chromosome is involved in Williams Syndrome?

A

7q

47
Q

Which chromosome is involved in Angelman Syndrome?

A

15q

48
Q

Which chromosome is involved in Prader-Willi Syndrome?

A

15q

49
Q

Which chromosome is involved in 22q11 Deletion Syndrome?

A

22q

50
Q

How is 22q11 Deletion Syndrome detected?

A

Typically via FISH

51
Q

What is the birth prevalence of 22q11 Deletion Syndrome?

A

1/4000

52
Q

What are other names for 22q11 Deletion Syndrome?

A
  • CATCH 22
  • Velocardiofacial (VCF) syndrome
  • Shprintzen Syndrome
  • DiGeorge Syndrome
53
Q

What occurs in 22q11 Deletion Syndrome?

A

~3Mb deletion of one copy of chromosome 22
- involves about 30 genes
= Failure to form derivatives of the 3rd and 4th brachial arches in embryonic development

54
Q

Which (deleted) gene is important in the phenotype of 22q11 Deletion Syndrome?

A

TBX1 gene

55
Q

What is the most common cause of the deletion in 22q11 Deletion Syndrome?

A

Deletion is de novo in 90-95% of cases, BUT inherited from an affected parent in 5-10%

56
Q

What is the mode of inheritance of 22q11 Deletion Syndrome?

A

Autosomal Dominant, variable expressivity (some cases mild, some very severe) - makes it difficult to counsel in prenatal cases

57
Q

What are the clinical features of 22q11 Deletion Syndrome?

A
  • Cardiac abnormalities (75%)
  • Thymus hypoplasia (immune abnormality) (75%)
  • Parathyroid hypoplasia (decreased Ca) (17-60%)
  • Palate abnormality (70%)
  • Distinctive facial features
  • Developmental delay (80%)
  • Adult onset schizophrenic episodes (~40%)
58
Q

What are some of the facial features seen in 22q11 Deletion Syndrome?

A
  • Big, cup-shaped ears
  • Tube nose
  • Long, slender fingers
59
Q

How should 22q11 Deletion Syndrome be managed?

A

Focus on the complications you are aware of!

  • Do echo and BP
  • Check thyroid and calcium levels
  • OT / physio / speech etc.
  • Ongoing management into adulthood for new complications
60
Q

What is important regarding vaccination of patients with 22q11 Deletion Syndrome?

A

Vaccines should be withheld!
Due to the T-cell abnormalities, they may have an abnormal response to vaccines. Only vaccinate once T-cell abnormality is ruled out.

Cardiovascular Block: Week 7 (5 decks)

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