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Pediatrics > Genetics > Flashcards

Genetics Flashcards

1
Q

Clinical features in Trisomy 21

A
  • Hypotonic
  • Flat occiput
  • Single palmar creases
  • Incurved fifth finger
  • Wide ‘sandal’ gap between the big and second toes
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2
Q

Complications in Trisomy 21

A
  • Learning difficulties
  • Congenital heard disease (present in 40%) - ECD (endocardial cushion defect (AV-canals)
  • Duodenal atresia
  • Impairment of vision (cataract) and hearing (secretory otitis media)
  • Hypothyroidism
  • Coeliac disease
  • Atlantoaxial instability
  • Epilepsy
  • Early onset Alzheimer disease
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3
Q

Causes of Trisomy 21

A
  1. Meiotic nondisjunction (94%)
    - Error at meiosis
    - Related to maternal age
  2. Translocation (5%)
    - Robertsonian translocation - a part of 21 is attached to another chromosome, usually 14
    - One parent may be a carrier
  3. Mosaicism (1%)
    - Some cells are normal, some have trisomy 21
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4
Q

What are the typical craniofacial appearance in Down’s?

A
  • Round face and flat nasal bridge
  • Upslanted palpebral fissures
  • Epicanthic folds
  • Brushfield spots in iris
  • Small mouth and protruding tongue
  • Small ears
  • Flat occiput and third fontanelle
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5
Q

What genetical abnormality is Edwards syndrome?

A

Trisomy 18

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6
Q

Clinical features of Edwards syndrome

A
  • Low birthweight
  • Prominent occiput
  • Small mouth and chin
  • Short sternum
  • Flexed, overlapping fingers
  • ‘Rocker-bottom’ feet
  • Cardiac and renal malformations
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7
Q

What genetical abnormality is Patau syndrome?

A

Trisomy 13

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8
Q

Clinical features of Patau syndrome?

A
  • Structural defect of brain
  • Scalp defect
  • Small eyes (microphthalmia) and other eye defects
  • Cleft lip and palate
  • Polydactyly
  • Cardiac and renal malformations
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9
Q

Genetics in Turner syndrome

A

45, X

  • 50% have one X
  • The others have deletion of the short arm of one X chromosome - isochromosome
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10
Q

Clinical features of Turner syndrome

A
  • Short stature!
  • Lymphedema of hands and feet
  • Neck webbing or thick neck
  • Cubitus valgus
  • Widely spaced nippels
  • CHD - coarctation of the aorta
  • Delayed puberty
  • Infertility
  • Hypothyroidism
  • Normal intellect
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11
Q

Treatment of Turner syndrome

A
  • Growth hormones

- Oestrogen therapy

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12
Q

Genetics in Klinefelter syndrome

A

47, XXY

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13
Q

Clinical features of Klinefelter syndrome

A
  • Tall stature!
  • Infertility
  • Hypogonadism with small testes
  • Gynecomastia in adolescence
  • Usually normal intelligence
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14
Q

Examples of syndromes caused by deletion

A
  • Cri-du-chat syndrome - deletion on chromosome 5
  • DiGeorge syndrome - deletion on chromosome 22
  • Williams syndrome - deletion on chromosome 7
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15
Q

What is mendelian inheritance?

A

Transmission of inherited traits or diseases caused by variation in a single gene

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16
Q

Examples of X-linked recessive disorders

A
  • Colour blindness
  • Duchenne and Becker muscular dystrophies
  • Fragile X syndrome
  • G6PD deficiency
  • Haemophilia A and B
  • Hunter syndrome
17
Q

How can the Fragile X syndrome affect females?

A

40-50 % of female carriers have learning difficulties - usually mild to moderate

18
Q

How many repeats is normalen, ‘premutation’ and ‘full mutation’ in fragile X syndrome?

A
  • Normal = about 45 repeats
  • ‘Premutation’ = 55-200 repeats (males can be unaffected but transmit condition further to grandsons)
  • ‘Full mutation’ = >200 repeats
19
Q

What is the most common genetic cause of learning difficulties?

A
  1. Down syndrome - most common

2. Fragile X syndrome - second most common

20
Q

Clinical features in Fragile X syndrome

A
  • Moderate - severe learning difficulties
  • Macrocephaly
  • Macroorchidism - postpubertal
  • Facies: long face, large everted ears, prominent mandible, broad forehead
  • Mitral valve prolapse
  • Joint laxity
  • Scoliosis
  • Autism, hyperactivity
21
Q

What does imprinting mean?

A
  • Expression of some genes is influences by the sex of the parent who transmitted it.
22
Q

The genetics of Prader-Willi syndrome

A

Absence of the functional paternal copy at the region 11 - 13 on chromosome 15
- Paternal chromosome responsible

23
Q

The genetics of Angelman syndrome

A

Absence of the functional maternal copy at the region 11 - 13 on chromosome 15
- Maternal chromosqme responsible

24
Q

Clinical features of Prader-Willi syndrome

A
  • Obesity - increased feeding and weight - binge eating
  • Short stature, small hands and feet
  • Hypotonia
  • Developmental delay, mild to severe mental retardation
  • Hyperphagia
25
Q

Clinical features of Angelman syndrome

A
  • Severe cognitive impairment
  • Characteristic facial appearance
  • Inappropriate laughter
  • Ataxia and jerky arm movements - ‘Happy Puppet syndrome’
  • Epilepsy
26
Q

VACTERL association

A 
V - Vertebral anomalies
A - Anal atresia
C - cardiac defects
TE - trecheoesophageal fistula
R - renal anomalies
L - limb defects (radial)
27
Q

Noonan syndrome

A
  • Autosomal dominant
  • Turner phenotype:
  • Characteristic facies
  • Mild learning difficulties
  • Short webbed neck with trident hair line
  • Pectus excavatum
  • Short stature
  • CHD - PULMONARY STENOSIS, atrial septal defect
28
Q

Pulmonic stenosis is common in which syndromes?

A
  • Noonan syndrome

- Alagille syndrome

29
Q

Williams syndrome

A
  • Deletion on chromosome 7
  • Clinical features:
  • Short stature
  • Face: Elfin facies
  • Transient neonatal hypercalcemia
  • CHD - Supravalvular aortic stenosis
  • Mild to moderate learning difficulties
30
Q

Endocardial cushion defect is common in which syndrome?

A

Trisomy 21 - Down’s syndrome

31
Q

Aortic stenosis is common in which syndrome?

A

Williams syndrome - supravalvular aortic stenosis

32
Q

Coarctation of aorta is common in which syndrome?

A

Turner syndrome

33
Q

Truncus arteriosis is associated with which syndrome?

A

CATCH-22 –> DiGeorge syndrome
Also seen:
* Transposition of the great arteries
* Aortic arch abnormalities

34
Q

Mitral valve prolapse is common in which syndromes?

A
  • Marfan syndorme

- Ehlers-Danlos syndrome

35
Q

CATCH-22 mnemonic

A 
C - Cardiac
A - Abnormal facies
T - Thymic hypoplasia
C - Cleft palate
H - Hypocalcemia (hypoplasia of parathyroid)
22 - micro deletion on chromosome 22
* DiGeorge syndrome
* Velocardial-facial syndrome
* Conotruncal anomaly face syndrome

Pediatrics (9 decks)

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