Paediatric Genetics Flashcards

1
Q

How do children normally get the additional chromosome in Down syndrome?

A

Additional chromosome 21 is commonly maternally derived from non-dysjunction

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2
Q

What screening tests should a baby with Down syndrome have done?

A
Cardiac echo
Feeding assessment - radiographic
Vision - red reflex as risk of cataracts
Thyroid - TSH and free T3/T4
Hearing - 90% have some level of hearing loss
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3
Q

What is the average life expectancy of a Down syndrome baby and how do they commonly die?

A

50yo

Most die of respiratory infection

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4
Q

What features of the head are indicative of Down syndrome?

A
Dysmorphic round face
Down slanting palpebral fissure
Flat nasal bridge
Epicanthic folds
Brushfield spots on iris
Small, low set ears
Flat occiput - brachycephaly
Protruding tongue - not macroglossia
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5
Q

What neck features are indicative of Down syndrome?

A

Abundant neck skin
Atlantoaxial instability
Hypothyroidism

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6
Q

What limb features are indicative of Down syndrome?

A

Incurved little fingers
Single palmar crease
Gap between 1st and 2nd toes

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7
Q

What other features are classical with Down syndrome?

A
Dislocations
Increased risk of leukaemia
Cardiac defects - 50%
Resp. infections
GI problems
Alzheimers disease
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8
Q

What cardiac defects are seen in Down syndrome?

A

VSD
Patent ductus arteriosus
ASD

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9
Q

What GI problems are seen in Down syndrome?

A

Duodenal atresia - double bubble on AXR

Higher risk of:
GORD
Hirschprung's
Meckel's
Coeliac
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10
Q

What is the place of antenatal screening in Down syndrome?

A

Its an optional screening program offered to all women

Should be counselled about the tests, risks, accuracy and what Down syndrome is

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11
Q

What is the aim of antenatal screening for Down syndrome?

A

Identify women at higher risk and offer further diagnostic testing

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12
Q

What further diagnostic testing can be done for Down syndrome?

A

Chrorionic villus sampling if <13 weeks

Amniocentesis if >15 weeks

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13
Q

What is the outcome of antenatal screening for down syndrome?

A

Expert counselling
Support
Offer termination

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14
Q

What is the process of antenatal screening for Down syndrome?

A

Serum free B-hCG (raised in Downs baby)
PAPP-A (lower in Downs baby)

USS to measure fetal nuchal translucency - increased in chromosomal abnormalities and heart failure

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15
Q

What is turners syndrome?

A

Loss or abnormality of an X chromosome in at least 1 cell line in a phenotypic female

45X

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16
Q

What 2 features characterise turners syndrome?

A

Short stature

Primary amenorrhoea

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17
Q

What features of turners syndrome would you see in a newborn?

A

Lymphoedema of hands and feet

Excessive skin at nape of neck

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18
Q

What features of turners syndrome would you see in an infant?

A

Feeding difficulty

Poor weight gain

19
Q

What other dysmorphic features are indicative of turners?

A

Webbed neck
Wide spaced nipples
Wide carrying angle
High arched palate
Epicanthic folds with downturned palpebral fissures
Pectus excavatum
Hearing loss - sensorineural/ottitis media with effusion

20
Q

What structural and functional abnormalities are seen in turners syndrome?

A

Gonadal dysgenesis
Congenital heart disease - coarctation, bicuspid aortic valve
Renal anomalies - absent, horseshoe or malrotated
Specific learning and behavioural disabilities
Hypertension
Autoimmune disorders

21
Q

How is diagnosis of turners syndrome made?

A

Prenatal - US scan
Birth appearance
Childhood changes
Adolescence

Diagnosis confirmation by chromosomal analysis

22
Q

How is turners syndrome managed?

A

MDT for all systems

Screening - thyroid, coeliac, hearing, ECG/echo
Bone age
Growth hormone therapy - in childhood - not if fused epiphysis
Oestrogen therapy - adolescence
Fertility - oocyte donation or embryo transplant

23
Q

What inheritance pattern is Duchenne Muscular Dystrophy?

A

X linked Recessive

Only affect males

New mutations are common so not all female relatives are carriers

24
Q

How common is Duchenne Muscular Dystrophy?

A

1 in 4000 males

25
Q

What is the pathophysiology of Duchenne Muscular Dystrophy?

A

Lack of dystrophin –> increased Ca entry into cell –> oxidative stress –> damage to sarcolemma and eventual cell death

26
Q

What does dystrophin normally do?

A

Connect muscle fibres to basal lamina - stabilise the plasma membrane

27
Q

What happens in the short term in Duchenne Muscular Dystrophy?

A

Muscles regenerate but fibres different sizes

28
Q

What eventually happens in Duchenne Muscular Dystrophy?

A

Myocyte apoptosis and creatine kinase release leads to a progressive muscle atrophy.

Fat and fibrotic tissue infiltrates muscle for pseudohypertrophy

29
Q

How does Duchenne Muscular Dystrophy present?

A
Symptoms occur by 3 years usually
Delay in development
Pseudohypertrophy of calf and tongue
Gower's sign
Waddling gait or tiptoe walking
Speech delay
Fail to thrive
30
Q

What parts of the body are affected in what order in Duchenne Muscular Dystrophy?

A

1 Hips, pelvis, thighs, shoulders
2 Arms, legs, trunk
3 Cardioresp

31
Q

What are some later effects of Duchenne Muscular Dystrophy?

A
Severe muscle weakness - wheelchair bound by 10-14yo
Type 2 resp failure
Scoliosis
Contractures
Dilated cardiomyopathy
Fatigue
Some may have learning disabilities
32
Q

How is Duchenne Muscular Dystrophy diagnosed?

A

Watch child!
Creatinine kinase raised (eventually drop)
Genetic testing
Muscle biopsy

33
Q

What is important to be aware of with Duchenne Muscular Dystrophy and anaesthetics?

A

DMD patients offer experience malignant hyperthermia and cardiac problems so anaesthetic use req. close monitoring

34
Q

What differentials may you consider for Duchenne Muscular Dystrophy?

A

Beckers muscular dystrophy - milder, progress more slowly
Polymyositis
Neurological causes - MS, spinal cord lesions etc.

35
Q

What is the general management for Duchenne Muscular Dystrophy?

A

MDT approach
Inform and support
Genetic diagnosis and counselling
Immunisations - flu and pneumococcal

36
Q

What is the management for children <11yo with Duchenne Muscular Dystrophy?

A

Physio
Knee-foot-ankle orthoses, serial casting ankles
Steroids - oral prednisolone
Calcium and vit D supplements

37
Q

What is the management for children with DMD between 8-11yo (once lost ability to walk)?

A

Mobility aids
Surgery for scoliosis
Cardiac and resp surveillance

38
Q

What is the management for the later stages of Duchenne Muscular Dystrophy?

A

Palliative care
Respire for family
End of life directives

39
Q

What respiratory complications are seen with Duchenne Muscular Dystrophy?

A

Hypoventilation - start during sleep
Lose cough - resp infections
Resp failure - often cause death

40
Q

What are the cardiac complications seen in Duchenne Muscular Dystrophy?

A

Cardiomyopathy
Congestive heart failure
Arrhythmias

41
Q

What gastro problems are seen in Duchenne Muscular Dystrophy?

A

Pseudo-obstruction

42
Q

What is important for the parents if their child has Duchenne Muscular Dystrophy?

A

Genetic counselling
Pre-natal genetic testing for subsequent pregnancies
They have increased risk of cardiomyopathy

43
Q

Why may carriers of Duchenne Muscular Dystrophy get skeletal muscle symptoms?

A

X-inactivation

Symptoms can be mild or as severe as DMD