Week 8-paediatric inherited conditions Flashcards

1
Q

What is the typical inheritance pattern of autosomal recessive diseases?

examples of autsomal recessive diseases?

A
  • for an autosomal recessive disease to be inherited both parents need to be carriers
  • of those children has a 1/4 or 25% chance of being affected
  • examples are cystic fibrosis and sickle cell disease
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2
Q

What is the most common inherited condition in the UK?

A

cystic fibrosis

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3
Q

What is the inheritance pattern of autosomal dominant diseases?

A

With autosomal dominant; one parent is a carrier and one is unaffected

Potential children, half will be unaffected, half will be affect and have the condition

Only one faulty copy required to have the disease –> 50% affected, 50% unaffected

Examples: AD PCKD, huntingtons

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4
Q

What is the inheritance pattern of recessive X linked disease when the father has the condition?

Examples of x linked recessive disease?

A
  • X linked recessive disease:
    • father has the condition (carrying affected X chromosome)
    • mother does not have the condition –> two working x chromosomes
    • sons –> all will be unaffected; sons inherit unaffected X chromosome from mother
    • daughters –> all daughters will be carriers, inheriting one affected X chromosome from the father
    • examples = beckers and duchenne’s muscular dystrophy
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5
Q

What is the inheritance pattern of X linked recessive disease when the mother is a carrier of the disease?

A
  • mother is a carrier with one affected X chromosome, and one healthy x chromosome
  • father is unaffected
  • potential inheritance pattern:
    • sons –> can inherit the unaffected X chromosome from mum and Y chromosome from dad OR can inherit the affected X chromosome from mum and unaffected Y chromosome (has the disease).
    • daughters –> can inherit unaffected X chromosome from mum and another unaffected from dad, or affected X chromosome from mum and unaffected X chromosome from dad (carrier).
    • 1/2 sons affected
    • 1/2 sons unaffected
    • 50:50 daughters carriers/ unaffected
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6
Q

What is the inheritance patterns of mitochondrial disease?

A
  • can only be inherited from mothers due to mitochondria contributing to the embryo only coming from the ovum.
  • often complex diseases
  • often rare
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7
Q

What type of chromosomal abnormalities can occur?

A
  1. Numerical –> trisomy (down’s syndrome Chromosome 21) or monosomy
  2. Structural –> duplication, deletion, translocation (unbalanced).
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8
Q

How common is down syndrome?

how is it detected ?

what are the typical features?

A

Trisomy 21 / down syndrome occurs in every 1/1000 births

detected by very sensitive antenatal screening

characteristic facial features

important internal features

later life complications

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9
Q

Gowers sign is linked with a particular genetic condition –> how is this condition inherited?

A

Gower’s sign = weakness of proximal muscles, particularly those of lower limb

patient has to use hands and arms to “walk up” their own body from squatting due to lack of thigh/ hip muscle strength.

Often seen in DMD (duchenne muscular dystrophy), DMD is X linked recessive disease

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10
Q

What are the characteristic facial and external features if down’s syndrome (trisomy 21) ?

A
  • Hypotonia
  • upward slanting palpebral fissures
  • brachycephaly –> flat occiput
  • clinodactyly with short 5th finger
  • protruding tongue
  • flat nasal bridge
  • epicanthal folds
  • brushfield spots (spots on iris)
  • ear abnormalities –> low set ears, stenotic meatus
  • single palmar crease
  • loose nuccal skin
  • short fingers
  • sandal gap
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11
Q

What are the important internal features of down syndrome?

A
  • AVSD (atrioventricular septal defect) , VSD (ventricular septal defect) , ASD (atrial septal defect).
  • hirschsprung’s disease (abscence of ganglions within the bowel leading to lack of peristalsis)
  • duodenal atresia
  • low IQ (Mean of 50)
  • ENT issues
  • hypothyroidism
  • atlanto-axial instability
  • Cataracts
  • TAM (transient abnormal myelopoesis) –> AML (acute myeloid leukaemia).
  • later in life –> early onset alzheimer’s (median age life expectancy 68 yrs)
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12
Q

What is Edward’s syndrome?

How common is it?

A

Edwards syndrome (trisomy 18) is a severe genetic disease.

Occurs in 1 in 3000-8000

not usually comptible with life (rarely gets to term, often spotaneous abortion).

50% of patients die by 1 week of life

90% of patients die by one year of life

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13
Q

What are the features of Edward’s syndrome?

A
  • Clenched hand with overlap of 2nd and 5th fingers over the 3rd and 4th
  • rocker bottom feet (prominent calcaneus and convex rounded bottom of foot).
  • micrognathia (undersized jaw), prominent occiput, micro-opthalmia
  • low set ears
  • VSD and ASD
  • generalised muscle spasticity
  • renal anomalies
  • mental retardation
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14
Q

What is patau’s syndrome?

A

Patau syndrome is the least common and most severe of the viable autosomal trisomies

caused by trisomy 13

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15
Q

How does patau’s syndrome normally present?

consistent features?

other features?

when is it generally recognised?

A

Many of the clinical features widely vary; however, severe mental deficiency is a consistent feature in children born with Patau syndrome.

Others:

  • Holoprosencephaly
  • polydactyly
  • flexion of the fingers
  • rocker-bottom feet
  • facial clefting
  • neural tube defects
  • heart defects

Patau syndrome is generally recognized at birth by the presence of structural birth defects and poor neurologic performance.

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16
Q

List the features of patau’s syndrome?

A
  • holoprosencephaly
  • polydactyl
  • seizures
  • deafness
  • mucrocephaly
  • midline cleft lip/ palate
  • abnormal ears
  • sloping forehead
  • cutis aplasia
  • omphalocele
  • cardiac and renal anomalies
17
Q

What are the two important sex chromosome conditions?

A

45, XO = Turner’s syndrome

47, XXY = Klinefelter’s syndrome

18
Q

What is the cause of turner’s syndrome?

A

Tuner’s sydrome: 45 XO

About half of individuals with Turner syndrome have monosomy X, which means each cell in the individual’s body has only one copy of the X chromosome

can also occur if one of the sex chromosomes is partially missing or rearranged rather than completely absent.

Some women with Turner syndrome have a chromosomal change in only some of their cells, which is known as mosaicism. Women with Turner syndrome caused by X chromosome mosaicism

19
Q

How does turner’s syndrome normally present?

A
  • Most commonly presents with short stature evident around age 5
  • early loss of ovarian function (premature ovarian failure or ovarian hypofunctino)
  • ovaries often develop but oocytes die prematurely and most ovarian tissue degenerates before birth
  • many girls do not undergo puberty without hormone therapy, most are infertile
  • Features:
    • low birth weight + length
    • short stature
    • low posterior hairline
    • webbed neck
    • puffy hands + feet (due to lymphoedema)
    • shield chest + wide spaced nipples
    • cubitus valgus –> elbows inward with forearms deviated outwards
    • short 4th metacarpal
    • high palate
    • low set ears
20
Q

What are the internal issues of turners syndrome?

A
  • some women with turner syndrome have a chromosomal change in only some of their cells which = mosaicism
  • mosaic turner syndrome caused by a random event during cell division in early fetal development
  • often affects endocrine organs –> gonadal dysgenesis, sexual infantilism ( lack of sexual development after puberty or delayed puberty) and hypothyroidism
  • cardiovascular issues –> coarctation of the aorta (detected by palpating femoral pulses); hypoplastic left heart, bicuspid aortic valve, essential hypertension
  • renal –> horshoe kidney, Pelvicoureteric junction obstruction, double collecting systems
21
Q

What is Klinefelter’s syndrome?

how common is it?

when does it present?

A

Extra sex chromosome, occuring only in males –> XY plus extra X (XXY)

1 in 600 male births

usually presents in adolescence

22
Q

How does klinefelter’s present?

A

muscle weakness

increased height

poor coordination

reduced body hair

gynaecomastia

reduced libido

primary hypogonadism –> low testosterone, high FSH

microorchidism (abnormally small testes), infertility

23
Q

What is williams syndrome?

what is it characterised by?

caused by?

A

Williams syndrome is a developemental disorder that affects many parts of the body

characterised by mild to moderate intellectual disability, outgoing/ engaging personality, distincitive facial features and cardiovascular problems

Caused by deletion of regions 26-28 on chromosome 7.

7 q (long arm of chromosome 7) 11. 23 ( region 11, locus 23)

24
Q

what are the characteristic facial features of william’s syndrome?

A

Characteristic elfin facies:

short nose broad nasal tip

small widely spaced teeth

small chin

wide mouth

puffy eyes

full cheeks full lips

can appear more gaunt as adult

25
Q

What are the features of williams syndrome?

A
  • supravalvular aortic stenosis
  • hypercalcaemia
  • diabetes
  • hypothyroidism
  • visuspatial and numerical difficulties
  • spoken language + music abilities
  • cocktail party chatter/ personality –> over friendliness, lack of fear with stranger, strong pro-social compulsion, excessive talkativeness, verbal fluency with extensive + expressive speech rich in vocabulary
  • elastin region
  • IQ differences
26
Q

What is the cause of prader willi syndrome?

how common is it?

A

prader will syndrome is caused by deletion of paternal 15 q 11- q 13

people normally inherit one copy of this chromosome from each parent, and only the paternal genes remain on due to genomic imprinting on the maternal copy. Therefore deletion of critical genes that are normally expressed on chromosome 15 and non expression in maternal chromosome 15 leads to prader willi.

occurs in 1 in 15000- 20000

27
Q

What are the characteristic facies of prader willi syndrome?

A

narrow temples

thin upper lip

elongated face

large nose

there is distinctive evolution of the condition and impaired hypothalamic function

early features:

  • hypotonia
  • failure to thrive
  • poorly developed genitals
  • developmental delay –> walking at 24 months enhanced VP skills
  • hyperphagia
  • tantrums –> psychosis

Later features:

  • central obesity (IHD, T2DM, OSA)
  • Short stature
  • hypogonadism –> incomplete, delayed or abnormal pubertal developement
  • men are thought to be infertile
  • intellectual disability
28
Q

What is Duchenne Muscular Dystrophy?

A

X- Linked recessive disorder

  • Absence of dystrophin, protein that anchors cytoskeleton to the ECM.
  • Causes necrosis and destruction of muscle fibres which are replaced with adipose tissue→pseudohypertrophy
  • Early onset, 3-4 years.

Symptoms:

  • Gower’s sign (pushing hands on legs to stand)
29
Q

Sickle cell disease

Pathophysiology and type of genetic condition

How does it present?

Testing?

What is it useful against?

A

Predominantly affects African/ Eastern Mediterranean descent

Autosomal recessive

Pathophysiology: Mutation in chromosome 11 (β-globin gene). Glutamic acid replaced w/ valine à 2 α-globin & 2 mutated β-globin subunits –> HbS

Presentation:

  • Infections
  • Anaemia
  • Severe pain episodes

Dx:

  • Pre-natal testing
  • Neonatal screening

If have mutated gene won’t get malaria