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Genetics Flashcards

(44 cards)

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1
Q

What chromosomal abnormality causes Patau’s syndrome?

A

Trisomy 13

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2
Q

What are the features of Patau’s syndrome?

A
  • Cardiac defects = VSD, PDA, dextrocardia
  • Microcephaly and brain defects
  • Microphthalmia (small eyes)
  • Other eye defects
  • Cleft lip/palate
  • Polydactyl
  • Omphalocele / Gastroschisis (abdominal wall defects)
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3
Q

What chromosomal abnormality causes Edward’s syndrome?

A

Trisomy 18

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4
Q

What are the features of Edward’s syndrome?

A
  • LBW
  • Small mouth/chin
  • Low-set ears
  • ‘Rocker-bottom’ feet
  • Overlapping fingers
  • Intellectual disability
  • Cardiac, renal and GI abnormalities
  • Omphalocele / Gastroschisis (abdominal wall defects)
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5
Q

What chromosomal abnormality causes Down’s syndrome?

A

Trisomy 21

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6
Q

What are the features of Down’s syndrome?

A
  • Characteristic facies
  • Hypotonia and short neck
  • Single palmar crease
  • ‘Sandal gap’ on feet
  • Short stature
  • Upslanting palpebral fissures
  • Flat occiput
  • Congenital heart defects in 40%
  • Omphalocele / Gastroschisis (abdominal wall defects)
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7
Q

What genetic abnormality causes Noonan’s syndrome?

A

Mutated RAS/Mitogen Activated Protein Kinase

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8
Q

What are the features of Down’s syndrome?

A
  • Webbed neck
  • Trident hairline
  • Pectus excavatum
  • Short stature
  • Pulmonary stenosis
  • Low IQ - most common cause
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9
Q

What genetic abnormality causes Prader-Willi syndrome?

A

Lacks paternal 15q

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10
Q

What genetic abnormality causes Angelman’s syndrome?

A

Lacks maternal 15q

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11
Q

What are the features of Prader-Willi syndrome?

A
  • Hypotonia
  • Hyperphagia
  • Almond-shaped eyes
    • Fat, floppy, flaccid
  • Hypogonadism
  • Obesity (in later childhood)
  • Epicanthal folds
  • Flat nasal bridge + upturned nose
  • Learning disability
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12
Q

What are the features of Angelman syndrome?

A
  • Cognitive impairment
  • Ataxia
  • Epilepsy
  • Abnormal facial appearance
  • Myoclonic seizures
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13
Q

What chromosomal abnormality causes Turner’s syndrome?

A

45 X

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14
Q

What are the features of Turner’s syndrome?

A
  • Lymphoedema of hands/feet in neonate
  • Short stature, spoon-shaped nails
  • Wide carrying angle
  • Thick or webbed neck
  • Infertility
  • Bicuspid aortic valve > Aortic coarctation
    • ESM over aortic valve
  • Delayed puberty / Infertility
  • Hypothyroidism
  • Omphalocele / Gastroschisis (abdominal wall defects)
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15
Q

What chromosomal abnormality causes Klinefelter’s syndrome?

A

47 XXY

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16
Q

What are the features of Klinefelter’s syndrome?

A
  • Infertility
  • Hypogonadism (small testicles)
  • Gynaecomastia
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17
Q

What genetic abnormality causes Fragile X syndrome?

A

CGG trinucleotide repeat expansion mutation (fragile) to the FMR1 gene

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18
Q

What are the features of Fragile X syndrome?

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A
  • IQ 20-80 (mean 50) – 2nd most common cause of low IQ after Down’s Syndrome
  • Macrocephaly
  • Macroorchidism
  • Characteristic facies
    • Large, low-set ears
    • Long, thin face
  • Other – autism, joint laxity, scoliosis
  • Mitral valve prolapse - common complication
19
Q

Define Malformation.

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A

Primary structural defect occurring during the development of a tissue/organ.

20
Q

Define Defomration.

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A

Abnormal intrauterine mechanical force that distorts a normally formed structure (e.g. oligohydramnios).

21
Q

Define Disruption.

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A

Destruction of a foetal part that may have initially formed normally.

22
Q

Define Dysplasia.

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A

Abnormal cellular organisation or function.

23
Q

Define Single System Defect.

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A

Single congenital malformations.

24
Q

Define Sequence.

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A

Pattern of multiple abnormalities occurring after one initiating defect - i.e. posterior urethral valves.

25
Define Association.
Group of malformations that occur together but in different combinations case to case.
26
Define Syndrome.
Multiple abnormalities occurring repeatedly in a consistent pattern, common underlying causal mechanism.
27
What are the signs and symptoms of foetal alcohol syndrome?
* Microcephaly * Absent philtrum * Cardiac abnormalities * Reduced IQ * IUGR * Small upper lip
28
What are the signs and symptoms of cigarette smoking in pregnancy?
* IUGR * Miscarriage * Stillbirth
29
What are the signs and symptoms of syphilis infection in a neonate?
* Rhinitis * Saddle-nose * Deafness (sensorineural) * Hepatosplenomegaly * Jaundice
30
What is the prognosis of Patau's syndrome?
* 80% die in first month of life * 90% by 1 year of age
31
What are the appropriate investigations for suspected Patau's syndrome?
* USS analysis in 2nd trimester * Chromosomal analysis from amniocentesis/cffDNA
32
What is the prognosis of Edward's syndrome?
Many will die in infancy → prolonged survival is possible
33
What are the appropriate investigations for suspected Edward's syndrome?
* USS analysis in 2nd trimester * Chromosomal analysis from amniocentesis/cffDNA
34
What is the prognosis of Noonan's syndrome?
* Penetrance varies greatly * From lethal prenatally to minimal morbidity
35
What is the management of Prader-Willi syndrome?
* Growth hormone if clinical evidence of growth failure * Management of feeding and obesity (i.e. lock cupboards)
36
What are the signs and symptoms of neonatal Turner's syndrome?
* Pyloric stenosis * Cardiac problems * Coarctation of aorta * *Bicuspid aortic valve* * *AS murmur = ESM over aortic valve* * Renal anomalies * Cystic hygroma - may resolve early → skin on the back of the neck
37
Name 3 trinucleotide repeat-expansion mutations.
* Fragile X syndrome * Myotonic dystrophy * Huntington disease
38
What is the chromosomal pathogenesis of Down's syndrome?
* **Meiotic non-disjunction** - linked to maternal age * Error at meiosis, pair of chromosomes 21 fail to separate (one gamete has 2 x 21 and one has none) * 94% * No need to examine parental chromosome * **Translocation** * Extra chromosome 21 is joined to another chromosome (usually 14) * Robertsonian translocation * 5% * Parental Chr analysis is recommended * Risk of recurrence 10-15% if mother is translocation carrier * **Mosaicism** * Milder phenotype, some cells are normal, and some have trisomy 21, formation of chromosomally normal zygote but non-disjunction at mitosis * 1%
39
What are the craniofacial signs of Down's syndrome?
* Round face * Flat nasal bridge * Epicanthic folds * Brushfield spots in iris * Small mouth * Small ears * Flat occiput * 3rd fontanelle * Short neck * Single palmar crease * Sandal-gap * Hypotonia
40
What are the medical problem present at birth in Down's syndrome?
* Congenital heart defects - 40% * Duodenal atresia * Hirschprung’s disease * Omphalocele ± umbilical hernia
41
What are the medical problem present later if life in Down's syndrome?
* Delayed motor milestones * Learning difficulty / Low IQ * Short stature * Secretory otitis media *(75%)* * Visual impairment *(25-50%)* * OSA *(50-75%)* * Increased disease chance: * Leukaemia *(not ALL)* * Hypothyroidism * Coeliac’s * Epilepsy * Early-onset Alzheimer’s * Joint laxity - *screen for atlantoaxial instability in those doing sports → risk of neck dislocation*
42
What congenital conditions are associated with Down's syndrome?
* Kostmann’s syndrome * Bloom syndrome * Fanconi syndrome / Diamond-Blackfan * NF1 * Li Fraumeni syndrome
43
What is the management of Down's syndrome at birth?
* Echocardiogram - *AVSD* * Evaluation by paediatricians - *duodenal atresia* * Genetic counselling * Early intervention programmes if developmental delay is present * Physiotherapy → *prevent abnormal compensatory movements for physical limitations* * OT → *fine motor and self-care* * SALT → *speech intelligibility and to manage language delay*
44
What is the management of Down's syndrome in children?
* Annual tests * Hearing test * Thyroid levels * Ophthalmic evaluation (up to 5 years then every 2 years) * Appropriate education with an individualised educational plan * Haemoglobin level for IDA * Monitor for symptoms of sleep apnoea * Monitor growth using updated Down’s syndrome growth charts
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