B6.015 Myositis - Big Case Flashcards Preview

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Flashcards in B6.015 Myositis - Big Case Deck (60):
1

epimysium

ECM proteins including collagen

2

perimysium

well defined layer of CT surrounding individual bundles of muscle fibers (fascicles)

3

endomysium

network of fine collagen fibers and other ECM proteins, separates fibers from each other

4

describe the size and orientation of adult male quadricep fibers

40-80 micrometers thick
may reach 10 cm in length
closely packed to each other and in transverse section are polygonal in shape

5

structure of the myocardium

striated as a result of arrangement of actin and myosin filaments in sarcomeres
smaller than skeletal muscle fibers (15 micrometers) and shorter (85-100 micrometers)
1-2 nuclei per cell (rather than many like skeletal)

6

intercalated disc

junction between two cardiac muscle cells, distinguishing feature
help transverse signal quickly

7

internal components of myocardium

more vascularized than skeletal muscle
more abundant mitochondria (40% of volume)
glycogen granules between myofibrils

8

what is myositis

inflammation of the muscles

9

what are the 2 classes of muscular injury

myopathic - damage myofibers directly
neurogenic - disrupt muscle innervation

10

discuss the pathological process of neurogenic muscular injury

nerve injury leads to denervation and atrophy of the nerve
surrounding nerves that are not damaged reinnervate myofibers and regenerate
*what was previously a mixed pattern of muscle groups now becomes a dual population, one type right next to the other rather that the interspersed pattern or normal tissue*

11

3 main primary inflammatory myopathies

polymyositis
dermatomyositis
inclusion body myositis

12

what types of features can polymyositis and dermatomyositis display

typical features of autoimmune inflammatory diseases, including associations with certain autoantibodies (HLA-DR)

13

what is dermatomyositis

systemic autoimmune disease
damage to small blood vessels contributes to muscle injury

14

general symptoms associated with dermatomyositis

vasculopathic changes seen as telangiectasias in nail folds, eyelids, and gums
dropout of capillary vessels in skeletal muscle
associated with aching pains in shoulders or hips
some weakness (proximal and symmetrical)

15

additional findings that may be associated with dermatomyositis

heliotrope rash
erythema in nail beds, knees, elbows
skin tightness (shiny, red)
ulcers at pressure points

16

what other pathology can be associated with dermatomyositis

malignancy
usually present within a short time of each other
occasionally, myopathy may precede diagnosis of tumor by months or years

17

pathogenesis of dermatomyositis

-deposition of complement MAC within cap beds
-upregulation of MHC-1 in myofibers
-B lymphocytes and plasma cells part of inflammatory infiltrate

18

genetic component of Caucasian juvenile dermatomyositis and polymyositis

HLA-B8
HLA-DR3
HLA-DQA1*** (most important)

19

autoantibodies associated with dermatomyositis

anti-Mi2
anti-Jo1
anti-P155/P140
-can all be associated with specific clinical features

20

what is polymyositis

adult onset inflammatory myopathy that shares myalgia and weakness w dermatomyositis, but lacks cutaneous features
DIAGNOSIS OF EXCLUSION

21

symptoms/findings of polymyositis

symmetric proximal muscle involvement
inflammatory involvement of heart and lungs
similar autoantibodies to dermatomyositis

22

immunologic basis of polymyositis

CD-8 positive cytotoxic T cells are prominent part of inflammatory infiltrate

23

lab test/ imaging studies used in diagnosing myositis

CBC
CK
ESR
serology (autoantibodies)
biopsy
EMG
MRI

24

why is MRI useful in myositis diagnosis

shows increased signal in relation to edema and inflammatory changes in subQ fat
helps determine a good place to take a biopsy
helps monitor therapy

25

what type of muscle do you want to biopsy in myositis?

one that is weakened and affected, but not "end stage" so that it is completely destroyed by fat and fibrosis

26

pattern of EMG findings in neuropathic disorders

fewer voluntary motor units available to respond to central drive
reduced recruitment
surviving motor units are larger than normal with increased fiber density near the electrode
BIGGER AMPLITUDE
RANDOM FIRINGS

27

pattern of EMG findings in myopathic disorders

total number of units is normal
force generated by units is reduced
amplitude is reduced, but overall pattern is normal

28

histo findings in generalized myositis

fiber irregularity
interstitial area contains inflammatory cells

29

specific histo findings of dermatomyositis

ischemic changes, especially on edges of bundles (edges have least vasculature and are most at risk)
"peri vesicular atrophy"

30

epidemiology of sporadic inclusion body myositis

most commonly acquired in patients over 50
more common in males
more insidious onset

31

what helps alert a clinician to the possibility of IBM

unresponsive to corticosteroid therapy
different pattern of weakness than other myositis types

32

pattern of weakness in IBM

proximal and distal
prominent weakness in quadriceps
weakness at wrists, fingers, and ankles
asymmetrical (non dominant more severe)
dysphagia

33

CK in IBM

normal or <10x normal

34

CK in polymyositis

>10x normal

35

epidemiology of polymyositis

female > male
common before age 50
acute or subacute onset w more rapid course

36

histo findings in IBM

inflammation, rimmed vacuoles, inclusions
seen well with trichrome

37

what is CK

creatine kinase, most widely used enzyme to diagnose and follow muscle disease
presents in highest concentration in serum w muscle injury
most sensitive indicator of muscle injury
best measure of course of muscle injury

38

what type of CK is in skeletal muscle

99% MM subtype, small amounts of MB

39

how can CK distinguish between myopathic and neurogenic muscular injuries

CK >1000 in myopathic
do not see high CK with neurogenic, cells get smaller but are not destroyed releasing CK

40

what is immune mediated necrotizing myopathy (IMNM)/ necrotizing autoimmune myopathy (NAM)

novel entity among inflammatory myopathies
necrotic muscle fibers associated with macrophage infiltration and numerous regenerating fibers (without lymphocytic infiltrates)

41

autoantibodies associated with IMNM

anti-SRP

42

other associations with IMNM

malignancy
statin treatment
active viral infection

43

weakness pattern of IMNM

proximal and severe

44

labs and treatment of IMNM

CK levels high (>3000)
poor response to steroids (like IBM)

45

what is granulomatous myositis

rare condition that may be a manifestation of sarcoidosis or isolated

46

presentation of granulomatous myositis

chronic proximal muscle weakness
rarely: acute myositis or palpable nodular type
may mimic IBM

47

treatment of granulomatous myositis

steroid treatment usually effective in isolated type
less effective in sarcoid

48

histology of granulomatous myositis

inflammation
multinucleated giant cells w peripheral nuclei

49

goals of treatment of myositis

improve muscle strength
avoid development of extra muscular complications
resolution of cutaneous manifestations in DM

50

1st line myositis treatment

glucocorticoids
improves strength and preserves muscle function
prednisone tapering for 9-12 months
no standard regimen

51

what are glucocorticoid sparing agents

steroid sparing immunosuppressive agents generally initiated along with glucocorticoids
reduce cumulative dose of steroids and diminish glucocorticoid induced morbidity

52

example glucocorticoid sparing agent

azathioprine

53

mechanism of azathioprine

purine analog and antimetabolite family of medication
disrupts RNA and DNA synthesis
response takes 4-6 months

54

adverse effects of azathioprine

systemic flue like reactions with fever and GI complaints (discontinue drug)
BM suppression, pancreatitis, liver toxicity
long term increased risk of malignancy

55

advantage of methotrexate

once a week administration

56

mechanism of methotrexate

inhibits DHFR to stop purine and pyrimidine synthesis

57

adverse effects of methotrexate

stomatitis, GI symptoms, leukopenia (minimized by giving folic acid)
potential hepatotoxicity (DO NOT DRINK)

58

IVIg use in myositis

for patients with life threatening weakness (Severe dysphagia with risk for aspiration)
rapid onset
prolonged treatment is limited by difficulty of admin, cost, and potential toxicity

59

use of antimalarial in myositis

hydroxychloroquine
effective in up to 75% of patients in controlling skin disease
no benefit for muscles

60

use of rituximab in myositis

targets CD20+, depletion of B cells within several weeks of admin
promising for treatment of recurrent/resistant DM and PM