Myositis Flashcards Preview

SBM IV CT/MS > Myositis > Flashcards

Flashcards in Myositis Deck (31):
1

Define polymyositis

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

2

explain the utility of testing CPK

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

3

explain the utility of EMG and nerve conducting testing in IIM

to differentiate myopathic and neuropathic disorders

to localize affected area and identify site for biopsy

4

describe EMG changes in inflammatory myopathy

generally, muscle is irritated

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

5

limitations of EMG testing for IIM

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

6

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

7

pathology in polymyositis

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

ICAM-1 expressed in muscle fibers

 

8

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endomysial inflammation w/ predominantly CD8 T cells in polymyositis

9

clinical features of dermatomyositis

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

10

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shawl sign in dermatomyositis

11

pathology of dermatomyositis

perimysial inflammation w/ CD4+ T cells

complement deposited of vessels

12

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perimysial inflammation w/ CD4 T cells in dermatomyositis

13

describe pathologic differences b/t polymyositis and dermatomyositis

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14

what auto-antibodies might you check for in IIM?

ANA (90%)

Jo-1 (20%)

SRP (5%)

Mi-2 (5-10%)

15

what is the most common extramuscular target organ of IIM?

lungs - interstitial pneumonitis, alveolitis, fibrosis

16

ENA panel

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

Anti-synthetase syndrome

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

strong assoc w/ interstitial lung disease

also, Raynaud's, arthritis, mechanic's hands

18

pulmonary manifestations of IIM

ILD: inflammation --> fibrosis

Muscle weakness --> impaired breathing

Pharyngeal weakness --> aspiration pneumonitis

19

relationship b/t malignancy and myositis

increased risk of malignancy in pts w/ PM and DM

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

20

3 subtypes of dermatomyositis

  1. adult dermatomyositis
  2. juvenile dermatomyositis
  3. amyopathic dermatomyositis

21

clinical features of juvenile dermatomyositis

similar to adult form + vasculitis, lipodystrophy, calcinosis

22

amyopathic dermatomyositis

typical rash of DM but w/ no muscle involvement

may later develop muscle involvement

may be assoc w/ malignancy (paraneoplastic?)

23

tx of PM and DM

primary: steroids

maintenance: methotrexate or axathioprine

 

24

inclusion body myositis clinical presentation

typically elderly males

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

no response to therapy, slow gradual decline in muscle strength

25

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inclusion body myositis

26

rhabdomyolysis

muscle necrosis w/ very high CPK levels

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

27

causes of drug induced myopathies

most common = statins

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

28

steroid myopathy

causes type II fiber atrophy rather than inflammation

29

polymyalgia rheumatica

-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

tx for polymyalgia rheumatica

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

taper down over months or couple years

31

Liver enzymes in IIM

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

NOT ALWAYS DUE TO LIVER PROBS