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Musculoskeletal 3.1 > Msk 10 > Flashcards

Msk 10 Flashcards

1
Q

ATPase at pH 4.2 stains light for________.

A

Type 2 muscle fibers

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1
Q

While the Dystrophin gene is the most related to Duchenne and Becker muscular dystrophies, what other genes are associated with the following muscular dystrophies:

Fascioscapulohumeral muscular dystrophy

Myotonic muscular dystrophy

Limb-Girdle muscular dystrophy

A

FSHD

DM1 & DM2

At least 25 subtypes

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1
Q

What are the most common muscular dystrophies found in adults? And how are they characterized?

A

Myotonic Dystrophies (DM1 & DM2)

Stiffness and myotonia (sustained involuntary contraction of muscles) - may not be able to release grip

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2
Q

What is the marker for muscle injury (lab)?

A

Elevated creatine kinase

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3
Q

ATPase at pH 9.4 stains light for __________.

A

Type 1 muscle fibers

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3
Q
A

Duchenne Muscular Dystrophy

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4
Q

A patient presents with symptoms of Becker’s Muscular Dystrophy; however, the genetic deletion contains the binding site on dystrophin to dystroglycan. Is this still Becker’s?

A

No. This pt cannot anchor contractile apparatus to the sarcolemma. This is Duchenne’s Muscular Dystrophy.

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5
Q

This disease occurs in both adults and children, with peaks at 10-15 and 45-60 years old.

A

Dermatomyositis

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6
Q

NADH light staining is indicative of ______.

A

Type 2 muscle fibers

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6
Q

DMD gene mutations are ___% new mutations and ___% deletions.

A

30% new

65% deletions

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6
Q

How is polymyositis different from dermatomyositis?

A

Vascular injury isnt major

No cutaneous involvement

Limited to adults

CD8 T cytotoxic cell mediated

Blood vessels are normal with no perivascular or perifasicular infiltration

CD8 T cell infiltration - endomysial

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7
Q

In a histological sample showing both degenerative and inflammatory changes characteristic of Inclusion Body Myositis, what else would be seen?

A

Inclusion bodies (vacuoles)

Cytoplasm contains intracellular protein deposits - similar to those found in Alzheimer disease

  • Amyloid-ß protein
  • Tau protein
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8
Q

What is the genetic cause of myotonic dystrophy DM2?

A

CCTG repeat in intron 1 of ZNF9 gene

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9
Q

Pt presents with:

Proximal symmetric muscle weakness

Elevated creatine kinase

Chronic perivascular and perimysial inflammatory myopathy

Perifasicular atrophy

Deposition of MAC or complement

A

Dermatomyositis - Myositis

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11
Q

Adult patient presents with chest pain and facial and oropharyngeal weakness (myotonia). The physician tells his med student that death is often a result of cardiac complications in these patients. What is the diagnosis?

A

Myotonic dystrophy DM1

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12
Q

DMD has the highest frequency of mutation, but does it have a higher adult prevalence than BMD?

A

No. DMD has high patient morbidity and early age of onset.

13
Q

In Myotonic Dystrophy DM2, myotonia may be minimal. What is the marked complaint of these patients?

A

Proximal muscle weakness

Also muscle pain and stiffness

14
Q

What 3 autoantibodies will yield positive tests for dermatomyositis?

A

Anti-nuclear antibody

Myositis-specific antibodies - Anti-Jo1

Dermatomyositis specific antibodies - Anti-Mi2

16
Q

NADH-TR dark staining is indicative of ______.

A

Type 1 muscle fibers

18
Q

What is the common response of myofibers to injury?

A

Necrosis

Mac’s penetrate BM

Satellite cells become myoblasts

Myoblasts fuse

Fibers are smaller & basophilic

18
Q

Does BMD result from an in-frame mutation or out-of-frame mutation?

A

In-frame

20
Q

ATPase at pH 9.4 stains dark for ___________.

A

Type 2 muscle fibers

22
Q

Denervation injury results in _______.

A

fiber grouping

22
Q

Does DMD result from an in-frame mutation or out-of-frame mutation?

A

Out-of-frame

and truncating mutations

23
Q

ATPase at pH 4.2 stains dark for ______.

A

Type 1 muscle fibers

24
Q

Which develops earlier in life: Duchenne’s or Becker’s muscular dystrophy?

A

Duchenne’s - birth

Becker - high prevalence due to longer lifespan

25
Q

Which inflammatory myopathy is associated with damage to small vesss in skin and muscle (C5-9 attack complex present)?

A

Dermatomyositis

26
Q

A CTG repeat in the DMPK gene causes_____.

A

Mytonic Dystrophy DM1

Indirect –> deficiency of chloride channel CLC1

27
Q

On the DMD gene, the actin binding region is found at which terminus?

A

Amino

Also 4 hinge regions

Cysteine domain (CRD)

Carboxy terminal domain (CTD)

24 spectrin-like repeats

29
Q

What are some genetic approaches to treat DMD?

A

Viral therapy

Termination codon read-through - Ataluren

Exon skipping (exon 51) - Prosensa, Sarepta

Increasing Utrophin levels - similar fxn to dystrophin

30
Q

What is the function of dystrophin?

A

Links actin to the extracellular matrix

Transfers force of muscle contraction to the CT

31
Q

Which form of myotonic dystrophy presents in adulthood (most common) or as congenital and child-onset forms?

A

DM1

33
Q

Which form of myotonic dystrophy is milder and presents in middle age?

A

DM2

34
Q

What is different about Inclusion Body Myositis from other idiopathic myositis syndromes?

A

Distal (not proximal) muscles are affected

  • knee extensors
  • wrist and finger flexors

Disease is slowly progressive and may be asymmetric

Affected individuals older than 50

CK levels only modestly elevated or normal

May be a specific autoantibody - anti-cN1A

Immunosuppressive resistant

35
Q

Pt presents with:

Heliotrope rash on eyelids with periorbital edema

Gottron papules on knuckles (scaly violet rash)

Photo-distributed violet rash

Calcinosis (calcium plaque on skin)

Interface inflammation in skin - similar to SLE (associated with comlement deposition)

A

Dermatomyositis - Dermal Disease

36
Q

What treatment can be used to delay DMD by about 2 years?

A

Corticosteroids

37
Q

Cellular damage in dermatomyosities is most likely mediated by what type of immune cells?

A

B cells

But both B and CD4 T helper cells are present in lesions

38
Q

Male pattern baldness

Temporalis muscle wasting (hatchet face)

Bilateral ptosis

Perioral weakness (fish mouth)

What are these features associated with?

A

Adult onset myotonic dystrophy DM1

Musculoskeletal 3.1 (14 decks)

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