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MM Test 1 > B6.015 Myositis - Big Case > Flashcards

B6.015 Myositis - Big Case Flashcards

1
Q

epimysium

A

ECM proteins including collagen

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2
Q

perimysium

A

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

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3
Q

endomysium

A

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

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4
Q

describe the size and orientation of adult male quadricep fibers

A

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

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5
Q

structure of the myocardium

A

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)

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6
Q

intercalated disc

A

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

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7
Q

internal components of myocardium

A

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

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8
Q

what is myositis

A

inflammation of the muscles

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9
Q

what are the 2 classes of muscular injury

A

myopathic - damage myofibers directly

neurogenic - disrupt muscle innervation

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10
Q

discuss the pathological process of neurogenic muscular injury

A

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

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11
Q

3 main primary inflammatory myopathies

A

polymyositis
dermatomyositis
inclusion body myositis

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12
Q

what types of features can polymyositis and dermatomyositis display

A

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

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13
Q

what is dermatomyositis

A

systemic autoimmune disease

damage to small blood vessels contributes to muscle injury

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14
Q

general symptoms associated with dermatomyositis

A

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)

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15
Q

additional findings that may be associated with dermatomyositis

A

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

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16
Q

what other pathology can be associated with dermatomyositis

A

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

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17
Q

pathogenesis of dermatomyositis

A
  • deposition of complement MAC within cap beds
  • upregulation of MHC-1 in myofibers
  • B lymphocytes and plasma cells part of inflammatory infiltrate
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18
Q

genetic component of Caucasian juvenile dermatomyositis and polymyositis

A

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

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19
Q

autoantibodies associated with dermatomyositis

A

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

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20
Q

what is polymyositis

A

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

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21
Q

symptoms/findings of polymyositis

A

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

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22
Q

immunologic basis of polymyositis

A

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

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23
Q

lab test/ imaging studies used in diagnosing myositis

A 
CBC
CK
ESR
serology (autoantibodies)
biopsy
EMG
MRI
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24
Q

why is MRI useful in myositis diagnosis

A

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

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25
Q

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

A

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

26
Q

pattern of EMG findings in neuropathic disorders

A

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
Q

pattern of EMG findings in myopathic disorders

A

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

28
Q

histo findings in generalized myositis

A

fiber irregularity

interstitial area contains inflammatory cells

29
Q

specific histo findings of dermatomyositis

A

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

30
Q

epidemiology of sporadic inclusion body myositis

A

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

31
Q

what helps alert a clinician to the possibility of IBM

A

unresponsive to corticosteroid therapy

different pattern of weakness than other myositis types

32
Q

pattern of weakness in IBM

A 
proximal and distal
prominent weakness in quadriceps
weakness at wrists, fingers, and ankles
asymmetrical (non dominant more severe)
dysphagia
33
Q

CK in IBM

A

normal or <10x normal

34
Q

CK in polymyositis

A

> 10x normal

35
Q

epidemiology of polymyositis

A

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

36
Q

histo findings in IBM

A

inflammation, rimmed vacuoles, inclusions

seen well with trichrome

37
Q

what is CK

A

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
Q

what type of CK is in skeletal muscle

A

99% MM subtype, small amounts of MB

39
Q

how can CK distinguish between myopathic and neurogenic muscular injuries

A

CK >1000 in myopathic

do not see high CK with neurogenic, cells get smaller but are not destroyed releasing CK

40
Q

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

A

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

41
Q

autoantibodies associated with IMNM

A

anti-SRP

42
Q

other associations with IMNM

A

malignancy
statin treatment
active viral infection

43
Q

weakness pattern of IMNM

A

proximal and severe

44
Q

labs and treatment of IMNM

A

CK levels high (>3000)

poor response to steroids (like IBM)

45
Q

what is granulomatous myositis

A

rare condition that may be a manifestation of sarcoidosis or isolated

46
Q

presentation of granulomatous myositis

A

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

47
Q

treatment of granulomatous myositis

A

steroid treatment usually effective in isolated type

less effective in sarcoid

48
Q

histology of granulomatous myositis

A

inflammation

multinucleated giant cells w peripheral nuclei

49
Q

goals of treatment of myositis

A

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

50
Q

1st line myositis treatment

A

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

51
Q

what are glucocorticoid sparing agents

A

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

52
Q

example glucocorticoid sparing agent

A

azathioprine

53
Q

mechanism of azathioprine

A

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

54
Q

adverse effects of azathioprine

A

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

55
Q

advantage of methotrexate

A

once a week administration

56
Q

mechanism of methotrexate

A

inhibits DHFR to stop purine and pyrimidine synthesis

57
Q

adverse effects of methotrexate

A 
stomatitis, GI symptoms, leukopenia (minimized by giving folic acid)
potential hepatotoxicity (DO NOT DRINK)
58
Q

IVIg use in myositis

A

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
Q

use of antimalarial in myositis

A

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

60
Q

use of rituximab in myositis

A

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

MM Test 1 (20 decks)

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