Pathology - Skeletal Muscle Pathology Flashcards

1
Q

Group of inherited muscle disorders leading to progressive weakness and muscle wasting

A

Muscular dystrophies

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2
Q

What are characteristics of muscular dystrophies?

A

Muscle fiber necrosis and regeneration

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3
Q

Most common muscular dystrophy?

A

Duchenne muscular dystrophy

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4
Q

Duchenne MD Etiology?

A
  • X-linked
  • LOF of dystrophin
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5
Q

Deletion or frameshift mutations result in ______ of dystrophin

A

total absence

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6
Q

What is dystrophin a key component of?

A

Dystrophin glycoprotein complex

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7
Q

What does the dystrophin glycoprotein complex do?

A

spans the plasma membrane - linking the cytoskeleton of the muscle fiber with the basement membrane

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8
Q

Defects in dystrophin glycoprotein complex leads to what?

A

Sarcolemma tears = ca influx from ECF = necrosis of muscle fibers

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9
Q

As Duchennes MD progresses, what replaces muscle tissue?

A

Collagen and fat cells

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10
Q

What is (+) Gower’s sign?

A

Patient has to push off of thighs in order to stand up

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11
Q

Where does weakness begin in Duchenne MD?

A

Pelvic girdle muscles and shoulder girdle

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12
Q

What can develop in older patients with Duchenne MD?

A

Cardiomyopathies and arrythmias

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13
Q

Duchenne diagnosis?

A
  • Progressive loss of creatine kinase
  • Genetic testing (definitive)
  • Muscle biopsies
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14
Q

Etiology of Becker MD?

A
  • X-linked
  • Truncated dystrophin due to mutation
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15
Q

Difference between Duchenne and Becker MD?

A

No dystrophin function in Duchenne, but partial function in Becker

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16
Q

definition of myotonia?

A

sustained involuntary muscle contraction

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17
Q

Inheritance pattern of myotonic dystrophy?

A

Autosomal dominant disorder caused by expansion of triplet repeats

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18
Q

Type I Myotonic Dystrophy?

A

Expansion of CGT tri-nt repeat in DMPK gene

19
Q

Type II Myotonic Dystrophy?

A

CCTG repeat expansion in CNPB gene

20
Q

Type I Myotonic Dystrophy Pathogenesis?

A

Toxic gain of function = disrupted splicing of mRNA transcript of other proteins, including transcript of chloride channel

21
Q

Type II Myotonic Dystrophy Pahtogenesis?

A

CNPB gene codes for a zinc-finger binding domain

22
Q

Is type I or type II myotonic dystrophy more sever?

A

type I more severe

23
Q

Patients with type I will also experience myotonia of what?

A

Involuntary muscles

24
Q

Where does type II myotonic dystrophy tend to affect?

A

Proximally located muscles (thigh or hip)

25
Most-common drug-related myopathy?
Statin myopathies
26
Pathophysiology of statin myopathies?
- decreased cholesterol may impact sarcolemma - depletion of CoQ10
27
Enzyme blocked by statins?
HMG-CoA reductase
28
Autoimmune condition associated with autoantibodies directed against acetylcholine receptors?
Myasthenia Gravis
29
There is a strong association between anti-Ach receptor autoantibodies and _____ abnormalities
thymic
30
What does the limit of the ability of the myofiber to respond to Ach at the neuromuscular junction do?
- impact turnover of Ach receptors - Blocks activation of Ach receptors - Damage neuromuscular junction
31
Common initial findings of MG?
Ptosis and diploplia
32
Redflag of MG?
Myasthenic crisis = Respiratory weakness becomes severe enough to necessitate intubation
33
Nearly all skeletal muscle tumors are _______
Malignant
34
Malignant mesenchymal tumour with skeletal muscle differentiation
Rhabdomyosarcoma
35
4 subtypes of Rhabdomyosarcoma?
Alveolar, Embryonal, Pleomorphic, spindle cell
36
Most common soft tissue sarcoma of childhood?
Alveolar and embryonal rhabdomyosarcoma
37
Most common soft tissue tumour in adolescents and young adults?
Synovial cell sarcoma
38
Syndrome of persistent widespread pain, stiffness, fatigue, disrupted sleep, and cognitive difficulties. It is often accompanied by anxiety/depression and impairment of activities of daily living
Fibromyalgia
39
Who is fibromyalgia most common in?
Young-adult to middle-aged females
40
What type of disorder is fibromyalgia considered?
Neurosensory disorder characterized in abnormalities in pain processing by the CNS
41
Fibromyalgia diagnosis?
WPI and self-administered patient questionnaire
42
Unexplained and profound fatigue that is worsened by exertion
Chronic Fatigue Syndrome
43
Who is mainly affected by chronic fatigue syndrome?
Young to middle-aged adult females
44
Diagnostic criteria for chronic fatigue syndrome?
- Fatigue - unrelated to exertion and not relieved by rest - Post-exertional malaise (PEM) - Unrefreshing sleep – fatigue despite a night’s sleep + either cognitive impairment and/or orthostatic intolerance