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Paediatrics > Paediatrics Genetics > Flashcards

Paediatrics Genetics Flashcards

1
Q

Where and on what is the genetic code located?

A

In the nucleus of every cell within a long string of nucleotides on a molecule called deoxyribonucleic acid (DNA)

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2
Q

How many chromosomes do we have and where are they?

A

23 chromosome pairs or 46 chromosomes in total

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3
Q

What are the sex chromosomes?

A

X chromosome and Y chromosome (males have X and Y and females have two X chromosomes)

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4
Q

What are the ‘other chromosomes’ called?

A

Autosomes (non-sex chromosomes)

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5
Q

What is the genotype and phenotype respectively?

A
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6
Q

What is the process of creating a gamete (egg or sperm) called?

A

Meiosis

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7
Q

How do the genes for Huntington’s Chorea and Cystic Fibrosis differ?

A

HC = dominant

CF = recessive

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8
Q

What are the possible chromosome disorders?

A

Deletion

Duplication

Mosaicism

Translocation

Trisomy

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9
Q

What is a deletion disorder?

A

Portion of a chromosome is missing (very rare)

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10
Q

What is an example of a deletion disorder?

A

Cri du chat caused by a missing portion of chromosome 5

Patients have learning, developmental and speech and language difficulties and characteristic “cat like cry”

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11
Q

Give an example of a duplication disorder?

A

Charcot-Marie-Tooth which can be caused by duplication of short arm of chromosome 17 - patients have sensory and motor neuropathy with characteristic pes cavus (high arching foot)

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12
Q

What are the types of translocation disorders?

A

One portion of chromosome is directly swapped with another portion

Reciprocal translocation = balanced

Nonreciprocal translocation = unbalanced

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13
Q

What can translocation disorders cause?

A

Predisposes to other conditions e.g. cancer or infertility

E.g. “philadelphia chromosome” translocation in acute myeloid lukaemia (reciprocal translocation between chromosomes 9 and 22)

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14
Q

What are Robertsonian translocations?

A

Occur in acrocentric chromosomes (13, 14, 15, 21, 22) with longer arm with most of the genetic material and short arm with little genetic information on it

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15
Q

What are the 3 trisomys?

A

Trisomy 13 = Patau syndrome (varies in severity) - learning disability, polydactylyl, microcephaly, cleft lip

Trisomy 18 = Edwards syndrome (varies in severity) - LD, micrognathia, overlapping of fingers, rocker bottom feet

Trisomy 21 = Down’s syndrome (most common)

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16
Q

What is mosaicism?

A

Scenario where the chromosomal abnormality happens after conception in a portion of cells in body and not in others - each is unique and effects are unpredictable

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17
Q

What are mitochondria?

A
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18
Q

What is mitochondrial inheritance?

A

At time of conception the sperm carrying the fathers genetic material enters the egg and the DNA in the nucleus of both cells combine.

All the mitochondria in this comes from mother at mitochondria in sperm is in tail which doesn’t enter the egg

Called maternal inheritance

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19
Q

What is diagnosis testing?

A

Testing a fetus or a person for a suspected genetic condition

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20
Q

Give an example of diagnostic testing?

A

Test fetus for a genetic condition via amniocentesis e.g. Down’s syndrome

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21
Q

What is predictive testing give an example?

A

Testing a person for a gene mutation e.g. BRAC1 breast cancer gene or gene for Huntington’s chorea

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22
Q

What is carrier testing, give an example?

A

Testing parent / potential parent for specific autosomal recessive condition e.g. cystic fibrosis gene

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23
Q

What are some other specific tests?

A

Genealogical testing

Forensic testing

Paternity testing

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24
Q

What are the ethical issues surrounding genetic testing?

A

Get consent

Give genetic counselling before and discuss implications

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25
Q

What is karyotyping?

A

Looking at number of chromosome - size and basic structure - helpful in diagnosing Down’s syndrome (trisomy 21) and Turner syndrome (45XO)

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26
Q

What is microassay testing?

A
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27
Q

When is microassay testing used?

A

Screening for chromosomal abnormalities and common genetic conditions

Looking for mutations in cancer cells and for research aimed at matching genes with phenotypes

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28
Q

What is specific gene testing?

A
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29
Q

What is DNA sequencing?

A

For research only - split the two strands of DNA and watch as individual nucleotides are added to a single strand of DNA - ultimately revealing the exact sequence

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30
Q

What are the dysmorphic features of Down’s syndrome?

A

Hypotonia (reduced muscle tone)

Brachycephaly (small head with a flat back)

Short neck

Short stature

Flattened face and nose

Prominent epicanthic folds

Upward sloping palpable fissures

Single palmar crease

31
Q

What are the complications of Down’s syndrome?

A

Learning disability

Recurrent otitis media

Deafness. Eustachian tube abnormalities lead to glue ear and conductive hearing loss.

Visual problems such myopia, strabismus and cataracts

Hypothyroidism occurs in 10 – 20%

Cardiac defects affect 1 in 3, particularly ASD, VSD, patent ductus arteriosus and tetralogy of Fallot

Atlantoaxial instability

Leukaemia is more common in children with Down’s

Dementia is more common in adults with Down’s

32
Q

What is the combined test?

A

Between 11-14 weeks

Maternal bloods (b-HCG and PAPPA - high and low indicate greater risk)

US (Nuchal thickness > 6mm indicates greater risk)

33
Q

What is the triple test?

A

Between 14-20 weeks

Maternal blood tests only:

  • b-HCG (higher)
  • AFP (lower)
  • Serum oestriol (lower)
34
Q

What is the quadruple test?

A

Performed between 14 and 20 weeks - identical to triple by includes maternal blood test for inhibin-A (if higher then indicates a greater risk)

35
Q

What if the risk score for Down’s syndrome is greater than 1 in 150?

A

Offer amniocentesis or chorionic villus sampling - take a sample of fetal cells for karyotyping

36
Q

How is chorionic villus sampling (CVS) performed?

A

Ultrasound guided biopsy of the placental tissue (done before 15 weeks)

37
Q

How is amniocentesis performed?

A

Ultrasound guided aspiration of some amniotic fluid using a needle and syringe - done later in pregnancy when there is enough amniotic fluid to make it safer to take a sample

38
Q

What is non-invasive prenatal testing (NIPT)

A

Maternal blood testing for fragments of fetal DNA - alternative to CVS/amniocentesis

39
Q

What is the management of Down’s syndrome?

A

By MDT:

  • OT
  • SALT
  • Physio
  • Dietician
  • Paediatricians
  • Cardiologists
  • ENT
  • Charities e.g. Down’s syndrome association
40
Q

What are the follow up investigations for Down’s syndrome?

A
  • Regular thyroid checks (2 yearly)
  • Echocardiogram to diagnose cardiac defects
  • Regular audiometry for hearing impairment
  • Regular eye checks
41
Q

What is the life expectancy for Down’s syndrome?

A

60 years

42
Q

What is Klinefelters syndrome?

A

Male has an additional X chromosome = 47 XXY (may have more Xs)

43
Q

What are the features of Kleinfelter syndrome?

A

Appear as normal males until puberty, then:

Taller height

Wider hips

Gynaecomastia

Weaker muscles

Small testicles

Reduced libido

Shyness

Infertility

Subtle learning difficulties (particularly affecting speech and language)

44
Q

What is the management for Kleinfelter syndrome?

A

No way to treat underlying genetic cause, treatment for features:

  • Testosterone injections improve many of the symptoms
  • Advanced IVF techniques have potential to allow fertility
  • Breast reduction surgery for cosmetic purposes
  • Speech and language therapy
  • OT for help with everyday tasks
  • Physio to strengthen muscles and joints
  • Educational support required for dyslexia and other learning difficulties
45
Q

What is the life expectancy with Kleinfelters?

A

Close to normal

46
Q

What is Turner’s syndrome?

A

Female has a single X chromosome making them 45 XO (life expectancy is close to normal)

47
Q

What are the features of Turner’s syndrome?

A

Short stature

Webbed neck

High arching palate

Downward sloping eyes with ptosis

Broad chest with widely spaced nipples

Cubitus valgus

Underdeveloped ovaries with reduced function

Late or incomplete puberty

Most women are infertile

48
Q

What conditions are associated with Turner’s syndrome?

A

Recurrent otitis media

Recurrent urinary tract infections

Coarctation of the aorta

Hypothyroidism

Hypertension

Obesity

Diabetes

Osteoporosis

Various specific learning disabilities

49
Q

What is the management of Turner’s syndrome?

A

Help with symptoms of condition

Growth hormone therapy to prevent short stature

Oestrogen and progesterone replacement to develop female secondary sex characteristics, regulate menstrual cycle and prevent osteoporosis

Fertility treatment to increase chances of becoming pregnant

50
Q

What is Noonan syndrome?

A

Genetic condition - number of different genes which cause it

Majority of cases are inherited in an autosomal dominant way

51
Q

What are the features of Noonan syndrome?

A

Webbed neck
Pectus excavatum
Short stature
Pulmonary stenosis

52
Q

What conditions are associated with Noonan syndrome?

A

CVD (pulmonary valve stenosis, ASD)

Cryptorchidism (undescended testes)

LD

Lymphoedema

Increased risk of leukaemia and neuroblastoma

53
Q

What is the treatment for Noonan syndrome?

A

Supportive with multidisciplinary team - main complication is congenital heart disease - often requiring corrective heart surgery

54
Q

What is Marfan syndrome?

A

Autosomal dominant condition affecting the gene responsible for creating firbillin (an important component of connective tissue) meaning that people with Marfan syndrome have features resulting from abnormal connective tissue

55
Q

What are the features of Marfan syndrome?

A

Tall stature

Long neck

Long limbs

Long fingers (arachnodactyly)

High arch palate

Hypermobility

Pectus carinatum or pectus excavatum

Downward sloping palpable fissures

56
Q

What are the two tests for arachnodactyly?

A

Cross their thumb across their palm (if tip goes over then arach)

Wrap finger and thumb around other wrist (if overlap then arach)

57
Q

What conditions are associated with Marfans?

A

Lens dislocation

Joint dislocation

Scoliosis of the spine

Pneumothorax

GORD

Aortic aneurym

58
Q

What is the management of Marfan’s?

A

Greatest risk = cardiac complications (valve prolapse and aortic aneurysms) - surgical correction

Manage risk = avoid intense exercise, caffeine, BBs, A2RB

Pregnancy = risk of aortic aneurysm

Physio

Yearly echo and ophthalmology

59
Q

What monitoring do patients with Marfan’s require?

A

Yearly echocardiograms and review by an ophthalmologist

60
Q

What is fragile X syndrome caused by?

A

Mutation in FMR1 (fragile X mental retardation 1 gene) - plays a role in cognitive development of the brain

61
Q

What is the pattern of inheritance of fragile X syndrome?

A

X-linked unclear if dominant or recessive - males are always affected but females affected to a varying level

62
Q

What are the features of fragile X syndrome?

A

Presents with a delay in speech and language development, along with:

  • Learning difficulties
    Macrocephaly
    Long face
    Large ears
    Macro-orchidism
63
Q

What is the management of fragile X syndrome?

A

Supportive, multi-disciplinary team to support:

  • Learning disability
  • Autism
  • ADHD
  • Seizures

Life expectancy is similar to general population

64
Q

What is Prada-Willi syndrome?

A

Loss of functional genes on the proximal arm of the chromosome 15 inherited from the father

65
Q

What are the features of Prada-Willi syndrome?

A

Hypotonia
Hypogonadism
Obesity

66
Q

What is the treatment of Prada-Willi syndrome?

A

No cure - carefully limit access to food (locking food in cupboards, putting lock on the fridge, controlling access to rubbish bins)

Growth hormone - improves muscle development and body composition

67
Q

Who is involved in the management of Prada-Willi syndrome?

A
  • Dieticians play in important role
  • Educational support
  • Social workers
  • Psychologists
  • Physiotherapists
  • OTs
68
Q

What is Angelman syndrome?

A

Loss of function of UBE3A gene on chromosome 15

69
Q

What are the features of Angelman syndrome?

A

Delayed development and learning disability

Severe delay or absence of speech development

Ataxia

Fascination with water

Happy demeanour

Inappropriate laughter

Hand flapping

Abnormal sleep patterns

Epilepsy

Attention-deficit hyperactivity disorder

Dysmorphic features

Microcephaly

Fair skin, light hair and blue eyes

Wide mouth with widely spaced teeth

70
Q

Who is involved in the management of Angelman syndrome?

A

Parental education

Social services and support

Educational support

Physiotherapy

Occupational therapy

Psychology

CAMHS

Anti-epileptic medication where required

71
Q

What is William syndrome caused by?

A

Deletion of genetic material on one copy of chromosome 7

Usually the result of a random deletion around conception

72
Q

What are the features of William syndrome?

A

Short stature
Learning difficulties
Friendly, extrovert personality
Transient neonatal hypercalcaemia
Supravalvular aortic stenosis

73
Q

What conditions are associated with William syndrome?

A

Supravalvular aortic stenosis

Hypercalcaemia

ADHD

HTN

74
Q

What is the management of William syndrome?

A

Echos and bp monitors to assess for aortic stenosis and hypertension

Low calcium diet required to control hypercalcaemia Avoid calcium and vit D supplements

Paediatrics (18 decks)

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