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CT.MS > Myositis > Flashcards

Myositis Flashcards

1
Q

What are the categories of myositis and myopathy?

A

Myositis, idiopathic
Rhabdomyolysis
Drug induced myopathy
Metabolic myopathies

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2
Q

What do you always want to make sure you rule out before giving a diagnosis of myositis?

A

Polymyalgia rheumatica

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3
Q

What are some of the idiopathic inflammatory myopathies?

A
  1. Polymyositis
  2. Dermatomyositis
  3. Inclusion body myositis
  4. Cancer related
  5. CT vascular disease-related
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4
Q

How do idiopathic inflammatory myopathies present?

A

Slowly progressive, fixed proximal weakness is the MAIN feature!

  • Fatigue
  • Elevated CPK
  • Aches, cramps, pains after exertion. BUT muscle pain is not the primary feature
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5
Q

What are the extra-musclar manifestations of inflammatory myopathies?

A

arthritis/raynaud’s pitting edema, pulmonary function decreased

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6
Q

What would you want to monitor for in someone with a diagnosis of inflammatory myopathy?

A

INCREASED RISK OF malignancy

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7
Q

What are the criteria for polymyositis?

A
  1. Symmetrical weakness of limb girdle muscles
  2. Biopsy shows necrosis/inflammation
  3. Elevation in serum/skeletal muscle enzymes
  4. EMG shows fibrillations/sharp waves
  5. derm findings
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8
Q

What would help you determine whether a patient’s muscle weakness was myopathic or neuropathic?

A
  1. Myopathic: proximal+symmetric. Normal neuro exam
  2. Neuropathic: can be asymmetric/distal.
    - Abnormal neuro exam
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9
Q

What are the relevant muscle enzymes?

A 
CPK 
Aldolase
AST
ALT
LDH
**AST and ALT are NOT solely liver enzymes!
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10
Q

What might cause a high CPK level?

A
  1. Acute MI
  2. Racial differences
  3. Trauma
  4. Exercise
  5. Drugs: ETOH, cocaine, statins, AZT
    Large muscle mass
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11
Q

What are the weaknesses of using CPK in idiopathic inflammatory mysositis?

A

CPK can be normal, and does not correlate with disease activity. Could be asymptomatic but have elevated enzymes

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12
Q

What would you use to differentiate between myopathic and neuropathic disorders?

A

EMG and nerve conduction. In myositis, EMG abnormal, nerve conduction study will be normal

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13
Q

What imaging would you want in myositis

A

Get an MRI

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14
Q

Describe what types of cells you would see in polymyositis and what cell surface receptors are involved

A

CD8+ T lymphocytes invade muscle fibers

  • CD45RO positive lymphocytes
  • ICAM-1 expressed on muscle fibers
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15
Q

How does polymyositis present?

A
  1. Gradual onset of fixed weakness in proximal muscle groups

2. Elevated muscle enzymes

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16
Q

What tests/imaging would you want to confirm the diagnosis of polymyositis?

A
  1. EMG and MRI

2. Muscle biopsy

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17
Q

Dermatomysositis: What’s different about this from polymyositis?

A

Think Polymyositis PLUS rash.

  • -However, muscle histology is different
  • -More likely to be a paraneoplastic syndrome
18
Q

What are the additional features of dermatomyositis?

A
  1. heliotrope discoloration of eyelids
  2. Periorbital edema
  3. Gottron’s sign: erythematous rash over MCP and PIP
  4. Rash over knees, elbows, medial malleoli
  5. Rash over face, neck, and upper torso
  6. capillary nailfuld changes + periungual erythema
19
Q

What is different about the histology of dermatomysitis as opposed to polymyositis?

A

Dermatomyositis: Inflammation is perivascular, while polymyositis has inflammation centered in the muscle

  • B cells predominate with CD4+ cells. In polymyositis, primarily CD8+ T cells and no B cells
  • Dermatomyositis has vasculopathy and complement deposition while polymyositis does not
20
Q

What is the most common auto-antibody in polymyositis and dermatomyositis?

A

ANA (90%) Sensitive, but not specific

–There’s also: Jo-1, SRP, and Mi-2

21
Q

What is the most common extramuscular target organ in idiopathic inflammatory myositis?

A

the LUNGs. Beware of aspiration pneumonitis, alveolitis, fibrosis (ILD)

22
Q

What does it mean if PM/DM is positive with ANA?

A

Nothing. It’s congruent with PM/DM but not specific. Could be indicative of another disorder

23
Q

What does it mean if PM/DM is positive for Ro/La antibodies?

A

Likely to be secondary to lupus/sjogren’s

24
Q

What does it mean if PM/DM is positive for Jo-1?

A

Specific to myositis. Targets anti-histidyl tRNA synthetase

25
Q

What does it mean if PM/DM is SRP positive?

A

Seen Seen with PM mostly. Indicates severe dz likely refractory to treatment

26
Q

What does it mean if PM/DM is Mi-2 positive?

A

More common in DM

27
Q

What is anti-synthetase syndrome?

A

PM/DM with anti-Jo-1

–>Strong association with interstitial lung dz

28
Q

Which cancers are most likely with PM and DM?

A

10-15% of getting:

Ovarian, lung, pancreatic, stomach, and CRC. Risk is greatest in the first three years

29
Q

Describe Juvenile dermatomyositis:

A

Like adult form PLUS

  1. Vasculitis
  2. Lipodystrophy
  3. Calcinosis
30
Q

Describe amyopathic dermatomyositis

A

Rash but everything else looks normal (strength, enzymes, histology). Assoc’d with malignancy

31
Q

How do you treat PM and DM?

A

Steroids

–Maintenance with methotrexate and azathioprine

32
Q

Describe inclusion body myositis

A

Seen in elderly males. No response in therapy. Histology shows rimmed vacuoles, inclusions, amyloid

33
Q

What would lead you to suspect rhabdomyolysis?

A

CPK 10,000-100,000

Caused by trauma/ischemia/hyperthermia/drugs/infection/metabolic

34
Q

What are the most common drug induced myopathies?

A 
Statins
Steroids (prednisone)
Cocaine
Alcohol
anti-malarials
35
Q

What do steroids do to muscles?

A

Mostly weakness. NOT inflammatory like statins, but mostly atrophy.

36
Q

What is different about metabolic myopathies?

A

Dynamic weakness, not fixed
Exercise intolerance
Myobloinuria
Multiple systems damaged (cardiac, neuro)

37
Q

What are causes of secondary metabolic myopathies?

A

Hypothyroidism

hypokalemia

38
Q

How does polymyalgia rheumatica present?

A

Dz of people over the age of 50

  • Rapid onset of hip and shoulder pain
  • inability to walk (MOSTLY PAIN not WEAKNESS)
39
Q

What is the cause of PMR? What labs would you see?

A

inflammatory condition of joints, not muscless. Elevated ESR/CRP but CPK is normal

40
Q

Should you work up minor elevations in CPK?

A

Maybe. It may not be pathologic b/c of differences in race, size, exercise capacity

41
Q

How do you treat PMR?

A

With steroids

CT.MS (13 decks)

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