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M&M Test 2 > B6-020 CBCL Muscular Dystrophy > Flashcards

B6-020 CBCL Muscular Dystrophy Flashcards

1
Q

what cell serves to repair damaged skeletal muscle cells?

A

satellite cell

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2
Q

connective tissue that surrounds the entire muscle

A

epimysium

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3
Q

connective tissue surrounding a fasicle

A

perimysium

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4
Q

connective tissue surrounding an individual muscle fiber

A

endomysium

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5
Q

calcium is very high in the

A

sarcoplasmic reticulum

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6
Q

helps connect the dystroglycan complex to the cytoskeleton in the muscle

A

dystrophin

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7
Q

centrally placed nuclei in skeletal muscle

A

myopathy

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8
Q

satelite cells lie under the

A

ECM

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9
Q

lack of dystrophin leads to

A

tears in the membrane

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10
Q

severity of muscular dystrophy is related to how much […] is present

A

dystrophin

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11
Q

myoblast that does not fuse to form the myotube

A

satelite cell

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12
Q

inheritance pattern of Duchenne and Becker md

A

X linked recessive

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13
Q

progressive difficulty rising from floor or chair

A

Gower’s sign

**apparent by age 3

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14
Q

normal milestones until child begins to walk

A

duchenne/becker

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15
Q

cardiopathy is more often associated with [duchenne’s or becker’s]

A

Beckers

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16
Q

tent-shaped mouth
nasal speech
ptosis
frontal balding with temporal wasting

A

DM1

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17
Q

muscle weakness is initially distal limb, facial, and axial
can spread proximally later on

A

DM1

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18
Q

associated with heart block and sudden cardiac death

A

DM1

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19
Q

caused by loss of function mutation in DMD

A

Duchenne

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20
Q

caused by mutation in DMD leading to truncated protein

A

Becker

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21
Q

links the cytoskeleton to the ECM via dystroglycan

A

dystrophin

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22
Q

describe the pathogenesis of Duchenne

A

deletions/duplications cause frameshift in DMD gene -> diminished mRNA synthesis of DMD gene -> low/absent dystrophin

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23
Q

describe the pathogenesis of Becker

A

deletions/duplication maintain reading frame of DMD gene –> synthesis of truncated mRNA for dystrophin –> synthesis of a partially functional, shorter dystrophin protein

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24
Q

80% of female carries for DMD mutations show […] despite being asymptomatic

A

elevated CK

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25
Q

caused by toxic gain of mRNA function mutation

A

DM1/2

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26
Q

caused by mutation in DMPK gene

A

DM1

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27
Q

caused by mutation in CNBP

A

DM2

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28
Q

severity of DM1 disease process is correlated to

A

number of repeats in mutated gene

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29
Q

is thought to sequester splicing proteins leading to globally altered mRNA splicing

A

DM1/2

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30
Q

tandem repeat numbers increase with each generation

A

anticipation

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31
Q

examples of trinucleotide repeat disease [2]

A

huntingtons
DM1/2

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32
Q

are steroids used to treat Duchenne/Becker?

A

Duchenne- yes, been shown slightly beneficial in ambulatory stages

Becker- not recommended

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33
Q

what is the issue in treating MD with gene therapy?

A

the gene is too big for vector

**micro-dystrophin

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34
Q

how does micro-dystrophin work?

A

smaller version of DMD gene that maintains the essential part of protein

this can be used to “convert” Duchenne pathogenesis to Becker

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35
Q

most commonly used RNA vector

A

lentivirus (HIV)

36
Q

most commonly used DNA vector

A

adenovirus

37
Q

how does antisense oligonucleotide therapy work?

A

ASO “masks” the splice site contained in the truncated mutation so that it is excised –> slightly shorter but functional mRNA

38
Q

RNA molecule that induces exon 51 skipping

A

eteplirsen

39
Q

which group in the eteplirsen trial showed the greatest decline in the 6MWT performance?

A

delayed treatment group after receiving the therapy

40
Q

premature stop codon therapy was first noted with

A

aminoglycoside antibiotics

**kill the bacteria by inhibiting protein translation

41
Q

allows insertion of amino acids at PTC rather than termination
results in greater fidelity of ribosome at true stop codon

A

PTC therapy

42
Q

MOA Translarna

A

PTC therapy

**not approved in US due to low evidence

43
Q

small deletion that allows retains the open reading frame resulting in a partially functional protein

44
Q

deletion that shifts the reading frame and results in loss of dystrophin

45
Q

caused by repeat expansions in DMPK and CNBP genes

46
Q

why do mature skeletal muscle cells have multiple nuclei?

A

individual myoblasts align and fuse their membranes together

47
Q

myotonia can be demonstrated by striking the […] with a reflex hammer

A

thenar eminence

48
Q

sharp adduction of thumb and firm contraction of thenar eminence upon percussion indicates

49
Q

ASO therapy (eteplirsen) is designed to treat what type of mutation?

A

pre mature stop codon in exon 51

50
Q

perimysium surrounds the

51
Q

endomysium surrounds

A

muscle fibers

52
Q

epimysium surrounds the

A

entire muscle

53
Q

myotonia is characteristic of

54
Q

cardiac conduction defects are more typically associated with

55
Q

MOA of micro-dystrophin

A

replacement of absent dystrophin

56
Q

what is the functional role of dystrophin?

A

links ECM through sarcolemma to cytoskeleton

57
Q

repeat expansions create mRNA with toxic GOF

58
Q

what is the inheritance pattern of myotonic dystrophy?

A

autosomal dominant

59
Q

histologic features of MD

A

variation of fiber size
fiber necrosis
fat/connective tissue proliferation
increased internal nuclei
no IHC staining for dystrophin

60
Q

inheritance pattern of trinucleotide repeat disorders

A

autosomal dominant

61
Q

in management of DMD, ensuring […] is necessary to prevent osteoporosis

A

calcium intake

62
Q

do DM patients typically lose the ability to ambulate?

63
Q

skeletal muscle results from the fusion of thousands of

64
Q

[…] cell has multiple nuclei

A

skeletal muscle

65
Q

how does X inactivation effect muscle cells?

A

each cell is formed by many myoblasts that each have randomly assigned X inactivation, so the cell will have aspects of both X chromosomes

66
Q

what are some symptoms of neuromuscular disease in infants?

A

arthrogryposis
hypotonia
feeding difficulties
respiratory problems

67
Q

what is the inheritance pattern of most GOF mutations?

A

autosomal dominant

68
Q

expected CK values of Becker/myotonic dystrophy

A

in the hundreds

69
Q

expected CK of Duchennes

A

in the thousands

70
Q

thumb abduction after percussion of the thenar eminence indicates

71
Q

used to treat DMD patients with a premature stop codon in exon 51

A

eteplirsen

72
Q

can eteplirsen reverse the damage that has already occurred?

A

no, can help slow progression but does not reverse

73
Q

role of dystrophin

A

link cytoskeleton to ECM via distroglycan

74
Q

dystrophin binds […] at its N terminal

75
Q

dystrophin binds […] at its C terminal

A

dystroglycan

76
Q

congenital DM1 is typically associated with a repeat length greater than

77
Q

can Becker be differentiated from DMD on histology?

78
Q

GOF mutations are generally [inheritance pattern]

A

autosomal dominant

79
Q

are steroids an effective therapy for MD?

80
Q

medication that decreases the rate of apoptosis of myotubes and decelerates myofiber necrosis in DMD

81
Q

used to treat heart failure that may arise in DMD

82
Q

is exercise shown to be beneficial in the management of MD patients?

A

no, deteriorating muscles can not strengthen and can accelerate disease course

83
Q

centrally placed nuclei on histology indicates

A

muscle cell degeneration and regeneration

84
Q

base pair mutation that leads to a premature stop codon

85
Q

the deletion maintains the reading frame

86
Q

deletion disrupts the reading frame leading to loss of protein

M&M Test 2 (18 decks)

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