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Systems: Specialities AB > Genetics: Multi-System Disease > Flashcards

Genetics: Multi-System Disease Flashcards

1
Q

Where do germline genetic variations present?

A

In every cell

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2
Q

What are the modes of inheritance in multi-system disorders?

A
  • All possible modes of inheritance

- Can include new mutations or inherited

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3
Q

Give examples of modes of inheritance and associated conditions

A

Chromosomal

  • Numerical: trisomy 21
  • Structural: translocations, deletions and microdeletions

Single gene disorders

  • Autosomal dominant: TS, NF1, Myotonic dystrophy
  • Autosomal negative: Cystic fibrosis
  • X-linked: Duchenne muscular dystrophy

Multifactorial
-Polygenic and environmental factors: hemochromatosis, diabetes

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4
Q

Why is there multi-system involvement with gene defects?

A
  • Several genes have diverse functions
  • Single genes can be widely expressed in different tissues
  • Single gene tissue-specific expression but tissue integral part of many systems
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5
Q

What are the common problems in establishing multi-system disease?

A

-Variable expression within as well as between families
-Present to a large variety if different specialities
-Family history is easily missed
-

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6
Q

What is the mode of inheritance for NF1?

A

Autosomal dominant

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7
Q

What is the prevalence of NF1?

A

1 in 2,500-3,500

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8
Q

What is the diagnostic criteria for NF1?

A

NIH diagnostic criteria, need 2+ for diagnosis:

  • Café au lait spots (6 or more)
  • Neurofibromas (2 or more)
  • Axillary freckling
  • Lisch nodules (specks in iris)
  • Optic glioma
  • Thinning of long bone cortex
  • Family history
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9
Q

What other clinical features can occur with NF1?

A
  • Macrocephaly
  • Short
  • Dysmorphic features (Noonan look)
  • Learning difficulties
  • Epilepsy
  • Scoliosis
  • Pseudoarthrosis of the tibia
  • Hypertension (renal artery stenosis, pheochromocytoma)
  • Neoplasia (CNS, optic gliomas, endocrine)
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10
Q

How is NF1 diagnosed?

A

Clinical diagnosis using diagnostic criteria

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11
Q

How is NF1 managed?

A
  • Annual review of affected individuals and at risk children until diagnosis can be excluded (5 years)
  • BP
  • Spine for scoliosis
  • Tibia for unusual angulation
  • Visual acuity and visual fields
  • Educational assessment
  • Ask patient to report any unusual symptoms
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12
Q

What is the genetics behind NF1?

A
  • Autosomal dominant
  • Variable expression
  • 17q gene (tumour suppressor gene) involved
  • Mutations different in different families
  • 50% due to new mutations, usually paternal in origin
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13
Q

What are the main features of NF2?

A
  • Bilateral acoustic neuromas
  • CNS and spinal tumours
  • A few CAL spots
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14
Q

Where is the gene implicated in NF2 located?

A

Chromosome 22

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15
Q

What is the classic triad of tuberous sclerosis?

A
  • Epilepsy
  • Learning difficulties
  • Skin lesions
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16
Q

What is the incidence of tuberous sclerosis?

A

1 in 7,000 newborns

17
Q

What is the mode of inheritance of tuberous sclerosis?

A

Autosomal dominant

18
Q

What tumour occurs in TS?

A

Hamartomas in different organs

19
Q

What is the genetics behind TS?

A
  • Autosomal dominant
  • 60% due to new mutations
  • Variable expression
  • Almost full penetrance
  • 2 genes on different chromosomes both cause TS (TSC1 +2)
20
Q

What are the clinical features of TS?

A
  • Multi-system
  • Variable expression (asymptomatic to severe mental and occasionally physical handicap)
  • Learning difficulty 40% :Autistic features common
  • Seizures 65% (including infantile spasms and myoclonic seizures)
  • Skin lesions
  • Cysts and angiomyolipmata in kidneys
  • Phakomas in eye
  • Rhabdomyomas in heart
21
Q

What skin lesions can occur in TS?

A
  • Depigmented macules
  • Angiofibromas
  • Fibrous plaque forehead
  • Shagreen patches
  • Ungual fibromas
22
Q

How should at-risk relatives of TS be screened?

A
  • Siblings and parents may be mildly affected
  • Surveillance and genetic counselling
  • Clinical examination (skin signs, including Woods lamp, nails), (retinal examination)
  • Cranial MR scan
  • Renal ultrasound
  • Echocardiogram
23
Q

What is the mode of inheritance of myotonic dystrophy?

A

Autosomal dominant

24
Q

What is the genetics behind MD?

A
  • Autosomal dominant

- CTG repeat, exhibits anticipation with increasing severity in each generation

25
Q

What is the clinical presentation of MD?

A
  • Bilateral late-onset cataract
  • Muscle weakness, stiffness and myotonia
  • Low motivation, bowel problems, diabetes
  • heart block
  • Death post-anaesthetic if not adequately monitored
  • Can have learning difficulties

Systems: Specialities AB (19 decks)

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