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SBM IV CT/MS > Myositis > Flashcards

Myositis Flashcards

1
Q

Define polymyositis

A
  • symmetrical weakness of limb-girdle muscles and anterior neck flexors
  • abnormal muscle biopsy
  • elevation in serum or skeletal-muscle enzymes
  • abnormal EMG
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2
Q

explain the utility of testing CPK

A

often tested in pts w/ idiopathic inflammatory myopathy, but may be normal and doesn’t correlate well w/ disease activity

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3
Q

explain the utility of EMG and nerve conducting testing in IIM

A

to differentiate myopathic and neuropathic disorders

to localize affected area and identify site for biopsy

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4
Q

describe EMG changes in inflammatory myopathy

A

generally, muscle is irritated

  • fibrillation at rest
  • high-freq repetitive discharges
  • polyphasic potentials of short duration and low amplitude
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5
Q

limitations of EMG testing for IIM

A

10% will have normal EMGs

abnormalities may be limited to paraspinous muscle

neuropathic findings may also be seen in:

  • inclusion body myositis,
  • myositis w/ anti-SRP antibodies
  • myositis and malignancy
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6
Q
A

MRI shows increased edema in affected area of muscle - marker of inflammation

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7
Q

pathology in polymyositis

A

cytotoxic CD8+ T lympocytes in muscle fibers - these express CD45RO

ICAM-1 expressed in muscle fibers

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8
Q
A

endomysial inflammation w/ predominantly CD8 T cells in polymyositis

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9
Q

clinical features of dermatomyositis

A

same as polymyositis: proximal muscle weakness +

derm findings: heliotrope rash, periorbital edema, Gottron’s sign (MCP, PIP), rash over knees/elbows/medial malleoli, rash on face/neck/upper torso (shawl sign, V-sign), capillary nail fold changes and periungual erythema

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10
Q
A

shawl sign in dermatomyositis

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11
Q

pathology of dermatomyositis

A

perimysial inflammation w/ CD4+ T cells

complement deposited of vessels

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12
Q
A

perimysial inflammation w/ CD4 T cells in dermatomyositis

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13
Q

describe pathologic differences b/t polymyositis and dermatomyositis

A
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14
Q

what auto-antibodies might you check for in IIM?

A

ANA (90%)

Jo-1 (20%)

SRP (5%)

Mi-2 (5-10%)

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15
Q

what is the most common extramuscular target organ of IIM?

A

lungs - interstitial pneumonitis, alveolitis, fibrosis

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16
Q

ENA panel

A

do an ENA if ANA is positive, b/c more specific

checks:

  • Jo-1: most common myositis specific
  • SRP: exclusively PM, if pos means severe type
  • Mi-2: more common in DM
17
Q

Anti-synthetase syndrome

A

PM or DM assoc w/ anti-Jo-1 antibody

strong assoc w/ interstitial lung disease

also, Raynaud’s, arthritis, mechanic’s hands

18
Q

pulmonary manifestations of IIM

A

ILD: inflammation –> fibrosis

Muscle weakness –> impaired breathing

Pharyngeal weakness –> aspiration pneumonitis

19
Q

relationship b/t malignancy and myositis

A

increased risk of malignancy in pts w/ PM and DM

strongest assoc w/ ovarian, lung, pancreatic, stomach, colorectal cancer

20
Q

3 subtypes of dermatomyositis

A
  1. adult dermatomyositis
  2. juvenile dermatomyositis
  3. amyopathic dermatomyositis
21
Q

clinical features of juvenile dermatomyositis

A

similar to adult form + vasculitis, lipodystrophy, calcinosis

22
Q

amyopathic dermatomyositis

A

typical rash of DM but w/ no muscle involvement

may later develop muscle involvement

may be assoc w/ malignancy (paraneoplastic?)

23
Q

tx of PM and DM

A

primary: steroids
maintenance: methotrexate or axathioprine

24
Q

inclusion body myositis clinical presentation

A

typically elderly males

weakenss: may be proximal and symmetric, distal, or asymmetric

no response to therapy, slow gradual decline in muscle strength

25
Q
A

inclusion body myositis

26
Q

rhabdomyolysis

A

muscle necrosis w/ very high CPK levels

many causes: traumatic ischemic, hyperthermic, drugs/toxins, infection, metabolic

27
Q

causes of drug induced myopathies

A

most common = statins

also, steroids, illicit drugs, alcohol, antimalarials, AZT

28
Q

steroid myopathy

A

causes type II fiber atrophy rather than inflammation

29
Q

polymyalgia rheumatica

A

-affects pts over age 50

rapid onset of hip and shoulder pain (rather than weakness)–> inability to walk or get up from sitting

inflammatory condition, but not of muscles

  • high ESR and/or CRP,
  • normal CPK
  • no autoantibodies
30
Q

tx for polymyalgia rheumatica

A

predisone 20mg daily or less –> dramatic and rapid improvement

taper down over months or couple years

31
Q

Liver enzymes in IIM

A

ASL and ALT may be elevated w/ injury or muscle inflammation

NOT ALWAYS DUE TO LIVER PROBS

SBM IV CT/MS (10 decks)

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