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Musculoskeletal Physiopathology > Noninflammatory & Congenital Myopathies > Flashcards

Noninflammatory & Congenital Myopathies Flashcards

1
Q

Are the following examples of myopathic or neurogenic muscle weakness?

  • Non-inflammatory etiology
  • Congenital
  • Inflammatory etiology
  • Myasthenia gravis
  • Metabolic disorders
A

Myopathic

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2
Q

Are the following examples of myopathic or neurogenic muscle weakness?

  • Spinal muscular atrophy
  • Type II fiber atrophy
  • Critical illness myopathy
A

Denervation (neurogenic)

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3
Q

Necrosis is a common response to ___ in primary muscle diseases

A

injury

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4
Q

What is an example of widespread muscle necrosis?
Segmental muscle necrosis?

A

Widespread: Rhabdomyolysis
Segmental: localized area ie. hamstring strain

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5
Q

If there is a single instance of injury to a muscle, how long until regeneration can restore normal structure and function of fibers?

A

Within a few weeks of single injury

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6
Q

Fiber necrosis and regeneration may occur at the same time with which disorders: acute, subacute, or chronic?

A

Subacute or chronic disorders

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7
Q

What does fiber necrosis and regeneration occurring simultaneously lead to?

A

Muscle fiber atrophy and fibrosis

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8
Q

What is the function of a satellite cell?

A

Maintenance of a muscle cell

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9
Q

segmental regeneration

First, the muscle fiber is injured, causing segmental disintegration of the ___

A

sarcoplasm

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10
Q

segmental regeneration

Once segmental disintegration of the sarcoplasm has occurred, what accumulates in the cell?
What is the function of this accumulation?

A

Macrophages accumulate and penetrate the basement membrane to phagocytose the sarcoplasmic contents

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11
Q

segmental regeneration

Which cells are responsible for penetrating the basement membrane to phagocytose sarcoplasmic contents after segmental disintegration?

A

Macrophages

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12
Q

segmental regeneration

After macrophages have begun phagocytosing the sarcoplasmic contents, which cells are activated?
What is the next function of those cells?

A

Satellite cells are activated and proliferate forming myoblasts

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13
Q

segmental regeneration

Satellite cells are activated by macrophages and proliferate to form myoblasts.
What follows the formation of myoblasts?

A
  • Macrophages leave with debris
  • Myoblasts align in the center of the fiber and begin to fuse
  • Fiber continues to regenerate until it appears normal
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14
Q

Is rhabdomyolysis inflammatory?

A

No

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15
Q

What is the etiology of rhabdomyolysis?

A

Skeletal muscle trauma (or side effect of statin drugs)

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16
Q

A patient has some swelling, tenderness, profound weakness in muscles, pain in joints, and fatigue. A biopsy is done of their muscle fibers. There is diffuse, widespread necrosis at varying degrees of regeneration. There are clusters of macrophages in and around muscle fibers. Evidence shows that sarcoplasmic contents have poured into circulation.
What is the likely diagnosis?

A

Rhabdomyolysis

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17
Q

Is rhabdomyolysis acute or chronic?

A

Can be acute, subacute, or chronic

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18
Q

How does muscle necrosis present with rhabdomyolysis?

A

Diffuse, widespread necrosis of muscle fibers; varying degrees of necrosis and regeneration throughout affected area

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19
Q

What are some risk factors for rhabdomyolysis?

A
  • Influenza
  • Metabolic myopathies
  • Alcoholism
  • Heat intolerance/stroke
  • Muscle necrosis (arterial occlusion, DVT)
  • Drugs (statins, cocaine, amphetamines)
  • Trauma, severe exertion
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20
Q

A patient presents fatigued with profound weakness in their muscles and diffuse pain which they describe as “joint pain”. You know they struggle with alcoholism and are taking statins for their hypercholesterolemia.
What diagnosis is likely?

A

Rhabdomyolysis

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21
Q

How does Hilton’s law relate to the “joint pain” experienced by those with rhabdomyolysis?

A

It’s not a joint problem, the joint shares innervation with the muscle that is the problem

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22
Q

If a patient has rhabdomyolysis, what may be elevated in their blood?

A
  • Creatine kinase (muscle breakdown)
  • Potassium
  • Creatine
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23
Q

What clinical manifestation of rhabdomyolysis may lead to acute renal failure?

A

Myoglobinuria (myoglobin dumped into urine damages kindeys)

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24
Q

A patient presents with muscle weakness and diffuse pain. Upon a blood test, creatine kinase, potassium, and creatine are elevated. Upon urinalysis, myoglobin is found in excess.
What is the likely diagnosis?

A

Rhabdomyolysis

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25
Q

What are some treatments for rhabdomyolysis?

A

Out of chiropractic scope:

  • Early and aggressive hydration (may prevent kidney damage)
  • Diuretics
  • Address hyperkalemia and low blood calcium levels
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26
Q

The prognosis for rhabdomyolysis varies depending on the extent of ___

A

kidney damage

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27
Q

Are muscular dystrophies inflammatory?

A

No inflammation

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28
Q

What is the frequent etiology of muscular dystrophy?

A

Hereditary/genetic

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29
Q

Is muscular dystrophy cureable?

A

No, it’s progressive

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30
Q

What are the general characteristics of muscular dystrophy?

A
  • Fiber necrosis with regeneration (imbalance)
  • Progressive fibrosis (eventual decreased contractility)
  • Infiltration by fatty tissue (marbling)
  • No inflammation
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31
Q

What are two X-linked muscular dystrophies?

A
  • Duchenne
  • Becker (less severe form of Duchenne)
32
Q

What is the mutation involved in Duchenne muscular dystrophy?

A

Xp21 gene mutation on X chromosome preventing dystrophin production
(X-linked recessive)

33
Q

How often is Duchenne muscular dystrophy spontaneous?
How common is Duchenne muscular dystrophy?

A

30% spontaneous somatic mutation
1 in 3600 live births

34
Q

Duchenne muscular dystrophy is passed through ___

A

heterozygous carriers (mother)

35
Q

How might a female carrier of Duchenne muscular dystrophy present?

A

2.5-25% will have symptoms (small percentage)

36
Q

Duchenne muscular dystrophy primarily affects which sex?

A

Males

37
Q

With Duchenne muscular dystrophy, the number of muscle fibers progressively decreases and is replaced by ___

A

fibrofatty connective tissue

38
Q

In which noninflammatory/congenital myopathy do we see pseudohypertrophy of the calves?

A

Duchenne muscular dystrophy

39
Q

Duchenne muscular dystrophy

Late stage, ___ fibers disappear almost completely, but ___ fibers are still numerous

A

extrafusal fibers disappear almost completely, but intrafusal fibers (spindle fibers) are still numerous

40
Q

Muscle weakness in children with Duchenne muscular dystrophy is detectable by ___ years of age

A

3-4
(pelvic and shoulder regions initially)

41
Q

What are some examples of lower limb involvement of Duchenne muscular dystrophy?

A
  • Pseudohypertrophy of calf muscles
  • Toe walk or waddling gait
42
Q

What are some clinical manifestations of Duchenne muscular dystrophy that occur in the spine?

A

Hyperlordosis and scoliosis

43
Q

A 3-year-old male patient is brought into the doctor by their parents. They report he is falling frequently, and has difficulty running, jumping, climbing stairs, and rising from the floor. You notice when the patient walks that he seems to be on his toes. Upon questioning, parents report he’s always had some gastrointestinal issues.
What is the likely diagnosis?

A

Duchenne muscular dystrophy

44
Q

Patients with Duchenne muscular dystrophy are generally ___ by age 10, and ___ by age 15

A

wheelchair bound by age 10, bedridden by age 15

45
Q

Death in those with Duchenne muscular dystrophy usually occurs as a result of ___

A

respiratory insufficiency (diaphragm involvement) or cardiac arrhythmia by approximately age 20

46
Q

What are some non-musculoskeletal clinical manifestations of Duchenne muscular dystrophy?

A
  • GI issues (smooth muscle impairment decreases motility)
  • Mild to moderate intellectual impairment
47
Q

If dystrophin presents as a truncated protein, as opposed to absent or nearly absent (as in Duchenne), what is the diagnosis?

A

Becker muscular dystrophy

48
Q

How does Becker muscular dystrophy compare to Duchenne?

A
  • Milder and later onset
  • Better neural function
49
Q

A patient presents with an exercise intolerance due to muscle cramping. They report symptoms of rhabdomyolysis and have evidence of myoglobinuria, however, they have a different pathology.
What is the likely diagnosis? What would confirm this?

A

Becker muscular dystrophy, confirmed by truncated protein (decreased quality) form of dystrophin

50
Q

Central core disease, rod myopathy, and central nuclear myopathy are all examples of ___

A

congenital myopathies

51
Q

How are congenital myopathies evident at birth?

A

“Floppy child” syndromes, lack of head control

52
Q

How do muscles present if affected by a congenital myopathy?

A

Hypotonia: decreased deep tendon reflexes, decreased muscle volume

53
Q

Spinal muscular atrophy (Werdnig-Hoffman disease) usually results in ___

A

death within first year of life (severe hypotonia)

54
Q

What are some complications of congenital myopathies evident in other body systems?

A

Pulmonary complications/weak respiration

55
Q

What is the condition with a chromosome 19 mutation of the gene that codes for ryanodine receptors?

A

Central core disease

56
Q

What sort of mutation is involved in central core disease?

A

Chromosome 19 mutation of gene that codes for ryanodine receptors

57
Q

What is the normal function of ryanodine receptors (RyR) in the muscle?

A

Help control calcium release from sarcoplasmic reticulum

58
Q

Is central core disease autosomal dominant or recessive?

A

Autosomal dominant

59
Q

Which fibers are primarily affected by central core disease?

A

Type I fibers (slow twitch/postural)

60
Q

Fibers involved in central core disease show a central area of degeneration
Is there associated denervation present?

A

Central lack of tissue, but no associated denervation present

61
Q

Central core disease puts individuals at higher risk for ___

A

malignant hyperthermia

62
Q

central core disease

What is the treatment for malignant hyperthermia?

A

Treatment with dantrolene: binds to ryanodine receptors
(reduced mortality from 80% to 10%)

63
Q

central core disease

Malignant hyperthermia occurs after ___ in susceptible individuals

A

anesthesia (halothane)

64
Q

What is the congenital myopathy where rod-like inclusions arise from the Z-band and accumulate in the sarcoplasm?

A

Rod myopathy

65
Q

What mutations are involved in rod myopathy?

A

Various mutations most commonly affecting nebulin

66
Q

Is rod myopathy inflammatory?

A

No

67
Q

Is denervation present in rod myopathy?

A

No

68
Q

Is rod myopathy progressive?

A

Non-progressive

69
Q

What is the best blood indicator of a muscle injury?

A

Increased serum creatine kinase

70
Q

What are some clinical manifestations of rod myopathy?

A
  • Hypotonia
  • Delayed motor milestones
  • Secondary skeletal changes (kyphoscoliosis)
  • Muscles of face, pharynx, and neck may be involved
  • Muscle degeneration (especially with later onset)
  • Increased serum creatine kinase
71
Q

What are the mutations involved in central nuclear myopathy?

A

Autosomal recessive or dominant mutations of dynamin 2

72
Q

central nuclear myopathy

Mutations of dynamin 2 influence which processes?

A
  • Endocytosis
  • Membrane function
  • Actin assembly
73
Q

How does central nuclear myopathy appear histologically?

A

Single, centrally located nucleus in skeletal muscle cells

74
Q

Where in the body does central nuclear myopathy have the most effects?
What is one of those effects?

A

Facial and extraocular involvement
Bilateral ptosis

75
Q

Which muscle fibers are predominantly affected by central nuclear myopathy?

A

Type I fibers

Musculoskeletal Physiopathology (32 decks)

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