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Year 3 - Genetics > Genetics - Multi-system Disease > Flashcards

Genetics - Multi-system Disease Flashcards

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1
Q

Multi-system disorders:

  • Many multi-system disorders have a ________ aetiology
  • Germ-line genetic variations present in every ____
A

genetic

cell

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2
Q

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

A

All possible modes of inheritance - new mutations or inherited

  • Chromosomal
  • Single gene disorders
  • Multifactorial
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3
Q

what are chromosomal modes of inheritance?

A

numerical eg trisomy 21

structural eg translocations, deletions and microdeletions

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4
Q

what are the different ways single gene disorders can be a mode of inheritance?

A

autosomal dominant eg TS, NF1, myotonic dystrophy

autosomal recessive eg Cystic fibrosis

X- linked eg Duchenne muscular dystrophy

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5
Q

what multifactorial ways can be a mode of inheritance?

A

polygenic

environmental factors:

  • haemochromatosis (nherited condition where iron levels in the body slowly build up over many years)
  • diabetes
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6
Q

Why multi-system involvement?

A

•Several genes with diverse functions are involved (chromosomal):

  • extra copies of some or many genes - trisomy, duplications
  • only single copies of some or many genes - monosomy, deletions, microdeletions (contiguous gene syndromes)
  • Single gene widely expressed in different tissues
  • Single gene tissue-specific expression but tissue integral part of many different systems
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7
Q

what are some common problems in multi-system disease?

A
  • Variable expression within as well as between families - sometimes difficult to predict phenotype from genotype
  • Present to a large variety of different specialists
  • Family history easily missed - often need to ask quite a wide range of questions to detect a positive FH

On the plus side - Considerable scope for screening and preventive interventions

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8
Q

Neurofibromatosis Type 1 (NF1) (Von Recklinghausen disease) - what is the epidemiology?

A
  • Autosomal dominant
  • Prevalence 1/2500 - 3500
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9
Q

how is a diagnosis of NF1 made?

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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10
Q

what are further features of NF1?

A
  • Macrocephaly (large head)
  • Short stature
  • Dysmorphic features- “Noonan look”
  • Learning difficulties - Most have some, often subtle, 10% special schooling, 3% moderate MH
  • Epilepsy
  • Scoliosis
  • Pseudoarthrosis of the tibia
  • Raised BP - due to renal artery stenosis or phaechromocytoma
  • Neoplasia - CNS (optic gliomas), endocrine
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11
Q

what is the Diagnosis of NF1?

A

•Clinical diagnosis using diagnostic criteria

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12
Q

what is the management of NF1?

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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13
Q

what is the genetics of NF1?

A
  • Autosomal dominant
  • Variable expression - inter-familial and intra-familial
  • Gene identified - 17q - tumour suppressor gene
  • Mutations different in different families - Test cost around £400 so used sparingly
  • 50% due to new mutations - usually paternal in origin
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14
Q

are NF1 and NF2 the same?

A

NF1 and NF2 are completely separate disorders!

Do not confuse NF1 and NF2

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15
Q

what are the main features of NF2?

A
  • acoustic neuromas »usually bilateral
  • CNS and spinal tumours
  • a few CAL spots

•NF2 gene is on Chromosome 22

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16
Q

what is Tuberous Sclerosis (TS)?

A

Tuberous sclerosis, also known as tuberous sclerosis complex, is a rare genetic condition that causes mainly non-cancerous (benign) tumours to develop in different parts of the body

  • Incidence 1 in 7000 newborns
  • Autosomal dominant
  • Hamartomas (noncancerous tumour) in different organs
17
Q

what is the classic traid of TS?

A

Epilepsy

Learning difficulty

Skin lesions

18
Q

what is the Genetics of TS?

A
  • Autosomal dominant - 60% due to new mutations
  • Variable expression - severity varies between family members
  • Almost full penetrance (if fully investigated) - gene carriers will have some signs even if only on scans
  • 2 genes on different chromosomes both cause TS with identical phenotypes:
  • TSC1
  • TSC2
19
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%:
  • infantile spasms
  • myoclonic seizures
20
Q

what are osme other features of TS?

A

•Skin lesions:

  • depigmented macules
  • angiofibromas
  • fibrous plaque forehead
  • hagreen patches
  • ungual fibromas
  • Kidney - cysts and angiomyolipomata
  • Phakomas in eye - benign unless on macula
  • Rhabdomyomas in heart
21
Q

pictures showing features of TS

A
22
Q

more pictures showing TS features

A
23
Q

what are the lcinical features of TS?

A
24
Q

how is Screening of at-risk relatives done?

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
25
Q

what is Myotonic dystrophy?

A

Myotonic dystrophy is a long-term genetic disorder that affects muscle function. It is a type of muscular dystrophy. Symptoms include gradually worsening muscle loss and weakness. Muscles often contract and are unable to relax. Other symptoms may include cataracts, intellectual disability and heart conduction problems

•Autosomal dominant

26
Q

what are the symptoms and features of Myotonic dystrophy?

A
  • CTG repeat, exhibits anticipation with increasing severity in each generation
  • Bilateral late-onset cataract
  • Muscle weakness, stiffness & myotonia
  • Low motivation, bowel probs, diabetes mellitus
  • Heart block
  • Death post-anaesthetic a risk if not monitored
  • Congenital myotonic dystrophy - Death / severe muscle disorder and learning difficulty
27
Q

Summary for multi-system genetic disorders:

  • Treat the _____ patient
  • Role for __________ specialist
  • Regular follow up if clinically _______
  • Remember _________ counselling
  • Variable ________
  • Understanding natural history allows early management of _________
A

whole

co-ordinating

beneficial

reproductive

expression

complications

Year 3 - Genetics (3 decks)

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