Inflammatory Myositis Flashcards Preview

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Flashcards in Inflammatory Myositis Deck (28)
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1
Q

What are the common clinical features of inflammatory myositis
?

A
  1. symmetrical, progressive proximal muscle weakness and/or pain
    - difficulty climbing stairs, getting out of the car, standing from seated
    - difficulty raising arms above head, combing hair
  2. constitutional symptoms may be present
2
Q

What is the epidemiology?

A

Rare 5-10 cases/1 million
More common in african americans
F:M, 2:1
mean age of onset 30-50

3
Q

What is the pathogenesis of polymyositis?

A

Autoimmune T cell mediated cytotoxic process against muscle Ags
CD8+ T cells and macrophages invade muscle fibres

4
Q

What is the link between Myositis and malignancy?

A

Incidence ~ 15%
Presents within 2 years of initial Dx
increased with anti-TIF1-gamma
mainly adenocarcinomas

5
Q

What are the characteristic features of Dermatomyositis?

A
Heliotrope rash (face)
Gottron's papules
V-neck sign
Shawl sign
periungal changes
- dilated nail bed capillary loops
- erythema
mechanics hands
6
Q

What is the pathophysiology of Dermatomyositis?

A

Myopathy differs from polymyositis as it is complement mediated
humeral attack against muscle capillaries and small arterioles
Activation of C3 -> formation of MAC
Capillaries are destroyed and muscles undergo microinfarction
CD4 postive T-cells

7
Q

What diagnostic tests are performed?

A
  1. CK - raised 5-50 times
  2. EMG - abnormal in 90%
    - decreased amplitude of motor potentials
    - fibrillation
    - complex repetitive discharges
  3. auto antibodies
    - myositis specific
    - CTD associated
  4. Muscle biopsy
  5. MRI - increased STIR signal indicated oedema due to inflammation - helps to guide site for biopsy
8
Q

What does the muscle biopsy show in polymyositis?

A

chronic inflammatory infiltrate surrounding the muscle fibres
variation in muscle fibre size
damaged fibres

9
Q

What myositis specific antibodies are found?

A

Anti-Jo-1
- associated with anti-synthetase syndrome
- associated with poor prognosis
Anti-Mi2
- associated with typical skin lesions of dermatomyositis
anti-TIF1-gamma and anti-NXP2 are associated with malignancy
Anti-SRP antibodies
- poor prognostic marker, increased cardiac involvement

10
Q

What are the different types of inflammatory myositis?

A
Polymyositis
Dermatomyositis
CTD associated myositis
Inclusion body myositis
Juvenile dermatomyositis
11
Q

What are some Ddx for myositis?

A
Drugs
- statins, alcohol
Endocrine myopathies
- hyper/hypothyroidism
Metabolic myopathies
Muscular dystrophies
Infectious
Paraneoplastic syndrome
neuropathy
Diabetic neuropathy
12
Q

What investigations should be performed to exclude malignancy in myositis?

A

FOB
mammography
pelvic USS in women
CT CAP usually done

13
Q

What does the anti-synthetase syndrome comprise of?

A
anti-Jo-1
myopathy
fever
ILD
Raynaud's
arthritis
mechanics hands
14
Q

What myositis associated auto antibodies can be found?

A

ANA
anti-Scl
- associated with polymositis/ scleroderma overlap
anti-SnRP
- Associated with myositis/connective tissue overlap
anti Ro/La
- associated with Sjogrens and SLE

15
Q

What is the typical pattern of clinical presentation of inclusion body myositis?

A
  • insidious onset of distal arm and proximal leg weakness
  • asymmetric
  • dysphagia is common with established disease
16
Q

What is the epidemiology of inclusion body myositis?

A

elderly men affected most commonly

20-30% have concomitant autoimmune disease

17
Q

What does the muscle biopsy show in inclusion body myositis?

A

endomysial inflammation
rimmed vacuoles
intracellular amyloid deposits

18
Q

What drugs can cause myopathy?

A
  • Alcohol
  • Antimalarials
  • Colchicine
  • Azole antifungals
  • Statins
  • D-penicillamine
  • Vincristine
  • AZT
19
Q

What antibody is associated with autoimmune necrotising myositis caused by statins?

A

anti-HMGCR

  • antibody against HMGCR - the target of statins
  • disease continues despite stopping the statin
20
Q

What is the treatment for dermatomyositis skin disease?

A
o	Sun avoidance, sunscreen
o	Topical steroids
o	Antimalarials (Doxycycline)
o	MTX
o	Mycophenalate
21
Q

How is myositis managed?

A
  1. initial treatment - steroids
    - if weakness is severe use 3-5 days IV steroids
    - 1-2 month taper
  2. If responds to steroids consider steroid sparing medication
    - AZA, MTX, Mycophenalate, Cyclosporine
  3. If disease does not respond to steroids (30%)
    - IVIg
  4. If does not respond to steroids + IVIg
    - ? diagnosis
    - Rituximab
  • Initial management is high dose steroids and MTX then add in IVIg if not doing well
22
Q

What idiopathic inflammatory myopathy is most associated with malignancy?

A

Dermatomyositis = 30%
Polymyositis = 15%
Inclusion body - no association with malignancy

23
Q

What are the most common cancers associated with Dermatomyositis/polymyositis?

A

Ovarian - main one

Cervix, lung, pancreas, bladder, stomach

24
Q

Factors indicating higher likelihood of malignancy?

A
Older age
rapid onset
Skin necrosis
peri-ungal erythema
low C4 levels
low lymphocyte counts
25
Q

Which myopathy is the least responsive to treatment?

A

Inclusion body myositis

26
Q

Which myopathy is most associated with humoral immunity?

A

Dermatomyositis

27
Q

Which myopathy is most associated with T-cell mediated immunity?

A

Polymyositis

Inclusion body myositis

28
Q

Elevations of CK in which inflammatory myopathies?

A

Polymyositis/dermatomysitis have modest elevations

IBM has mild or normal CK