02-27 Myositis Flashcards
OBJECTIVES 1. Appreciate the differences between inflammatory myositis, steroid myopathy, and polymyalgia rheumatica (PMR). 2. Appreciate the pathologic changes in PM/DM/IBM. 3. Know at least 5 causes of myopathy or myositis that are not PM/DM.
1
Q
OBJECTIVE #3: Know at least 5 causes of myopathy or myositis that are not PM/DM (i.e. list DDx/categories muscle problems)
A
- Other Myosites (a.k.a. idiopathic inflammatory myopathies)
- Inclusion body myositis
- Cancer related myositis
- Rhabdomyolysis
- Drug induced myopathy (especially steroid induced, ?statins–he didn’t mention)
- Metabolic myopathies
- PMR (polymyalgia rheumatica)
2
Q
S/Sx of Myositis (i.e. Idiopathic Inflammatory Myopathies)
A
SIGNS/SYMPTOMS
- Slowly progressive, fixed (i.e. all the time) proximal muscle WEAKNESS is dominant feature
- Muscle pain is probably NOT myositis
- even though we usu. think about
- Premature fatigue
- signif. decline in their level of activity
- Post-exertional aches, cramps and pains
- Chronic myalgias are not a primary feature
- Increased risk of malignancy
- We don’t know if myositis causes cancer or prediposition to cancer causes myositis
- May have arthritis, Raynaud’s, pitting edema of the extremities, pulmonary involvement
3
Q
- Enzyme tests to order?
- Reasons for false positives
A
- ENZYMES TESTS TO ORDER
CPK (most commonly measured)
Be worried when > 400
- Also checked in ?MI
- Can also be raised in:
- Racial differences
- Trauma: sharp or blunt (even just biopsy or EMG needle!)
- Post-exercise
- Really muscular person
- Drugs: ETOH, cocaine, statins, AZT
- Genetics
- Glycogen storage disease
- Muscular dystrophy
- Periodic paralysis
- Malignant hyperthermia
- Benign hyper-CK-emia
Other Enzymes
- Aldolase
- “Liver enzymes”
- AST – Aspartate aminotransferase
- ALT – Alanine aminotransferase
- LDH – Lactate dehydrogenase
4
Q
Causes for CPK false positives
A
CPK can also be raised in:
- Racial differences
- Trauma: sharp or blunt (even just biopsy or EMG needle!)
- Post-exercise
- Really muscular person
- Drugs: ETOH, cocaine, statins, AZT
- Genetics
- Glycogen storage disease
- Muscular dystrophy
- Periodic paralysis
- Malignant hyperthermia
- Benign hyper-CK-emia
5
Q
What antibodies should you order when considiering a Dx of PM/DM?
A
- ANA – broadly interacts with nuclear proteins, not specific (+ in ~90% cases)
- Ro, La, RNP – suggests that myositis is secondary to other autoimmune condition (lupus, Sjogren’s).
- Jo-1 – Most common myositis specific antibody (+ in ~20% cases)
- targets anti-histidyl tRNA synthetase (anti-synthetase syndrome)
- Anti-synthetase syn strongly assoc’d w/ ILD*, also: Raynaud’s, arthritis, mechanic’s hands.
- *keep an eye on their pulm status!
- targets anti-histidyl tRNA synthetase (anti-synthetase syndrome)
- SRP – Almost exclusively with PM (+ in ~5% cases)
- portends a severe myopathy, refractory to tx
- Mi-2 – More common in DM (+ in 5-10% cases)
6
Q
Dx Criteria for Myositis
A
From 1975 paper, still used, problem: doesn’t include imaging
- Symmetrical weakness of limb-girdle muscles and anterior neck flexors.
- Muscle biopsy evidence of necrosis of Type I and II fibers, phagocytosis, regeneration, variation in fiber type with inflammatory exudation.
- Elevation in serum or skeletal-muscle enzymes.
- Electromyographic triad of short, small, polyphasia motor units, fibrillations and sharp waves; and bizarre, repetitive discharges.
- Dermatologic features.
7
Q
EMGs
- Utility
- How sensitive/specific?
A
- Utility: differentiate between neuropathic and myopathic dz
- Sensitivity/Specificity
- About 40% will have all classic features
- EMGs are entirely normal in 10%
- Abnormalities may be limited to paraspinous muscles
- Mixed neuropathic-myopathic findings may also be seen in
- Inclusion body myositis
- Myositis with anti-SRP antibodies
- Myositis and malignancy
8
Q
Imaging for Myositis?
- What modality?
- What’s the utility?
A
See edema esp w/ T2-weight “STIR image”
- Helps you decide where to biopsy
9
Q
Weakness 2° Myopathic vs. Neuropathic vs. Pain
A
Myopathic
- Proximal and symmetric
- Remainder of neurologic exam normal
Neuropathic
- Proximal, distal and/or asymmetric
- Other abnormalities on neuro exam
Pain
- Sometimes pts describe inability to move b/c of pain as “weakness”
- Example: pt w/ severe polyarticular gout mis-dx as having GBS
10
Q
DZ: Polymyositis
- Presenting S/Sx
- Biopsy findings?
- Work-up/dx?
A
Presenting S/Sx
- Gradual onset of fixed weakness in proximal muscle groups.
- May be some component of myalgias, usually post-exertional.
Biopsy Findings
- [See image here] black dots = lymphocytes which would stain for:
- Cytotoxic CD8+ Ts invading muscle fibers (vs. dermatomyositis where you see what?)
- Invading lymphocytes express CD45RO (antigen primed memory cells)
- ICAM-1 expressed on muscle fibers
Work-Up/Dx
- Rule out confounders (neuro dz, muscular dystrophies, etc.)
- ↑ muscle enzymes.
- Supportive EMG and MRI
- Muscle biopsy confirms dx
11
Q
Name this here queen
A
Jinkx Monsoon, Season 5 Drag Super Star
“It’s Monsoon Season!”
12
Q
Name this queen, all-star Cher impersonator and Winner of RuPaul’s Drag Race All-Stars?
A
Chad Michaels
13
Q
DZ: Dermatomyositis
- Presenting S/Sx
- Biopsy findings?
- Work-up/dx?
- Subsets + Their Characteristics
A
Presenting S/Sx
- Polymyositis plus rash
- heliotrope rash (Lilac discoloration of eyelids)
- Periorbital edema
- Scaly, erythematous rash over MCP and PIP joints (Gottron’s sign)
- Rash over knees, elbows, medial malleoli
- Rash over face, neck, and upper torso
- shawl sign (back)
- V-sign (neck) [IMAGE HERE]
- Capillary nail fold changes and periungual erythema
- ?actually a separate dz
- ?more likely to be a paraneoplastic phenomenon
- though PM also definitely assoc’d w/ cancer
Biopsy Findings (See image here)
- Muscle histology is different
- B lymphocytes, plasmacytoid dendritic cells, and CD4+ T lymphocytes close to vessels
- Loss of capillaries and perifascicular atrophy
- Activated terminal components of complement deposited on vessels
- ICAM-1 on vessels
Work-Up/Dx
- .
Subsets + Their Characteristics
- Adult DM (as above)
- Juvenile DM = Adult + …
- …Vasculitis
- …Lipodystrophy (usu face)
- …Calcinosis
- Amyopathic DM
- Just the rash
- Nl strength, enzymes, histo
- May become typical
- Higher risk of malig
14
Q
- What other disease have this nail finding of increased erythema around the nail bed?
A
Diseases w/ nails like this include:
- Dermatomyositis
- Scleroderma
- ~Sometimes lupus
Nails Capillary Changes under magnifying glass:
- Normal capillaries, w/ fine uniform
- Early on: dilation of capillaries
- drop-out w/ incr dilation and minor hemorrhages
- more advanced
When you see these in the setting of weakness think: dermatomyositis!
- But again, also scleroderma and lupus
15
Q
Path differences between PM & DM
A
PM
- Inflammation centered in the muscle fascicles.
- Primarily CD8+ T cells, lack of B cells.
- No vasculopathy
DM
- Inflammation peri-fascicular (primarily near blood vessels)
- B cells predominate, also CD4+ T cells.
- Vasculopathy and complement deposition present
18
Q
DZ: Inclusion Body Myositis
- Presenting S/Sx
- Tx?
- Biopsy findings?
- Natural Hx?
A
PRESENTING S/SX
- Typically elderly males – very rare
- Weakness
- Proximal and symmetric
- Distal
- Asymmetric
TREATMENT
- No Response to Therapy
NATURAL HX
- Slow, gradual decline in muscle strength, though it may plateau.
- Die of aspiration pneumonia b/c of weak bulbar muscles, e.g.
BIOPSY FINDINGS
- Cellular infiltrate
- like PM but disappears
- Rimmed vacuoles
- Inclusions (see photo here)
- Amyloid deposits
- Mitochondrial abnormalities
24
Q
Bx Dx here?
A
Polymyositis
- black dots = lymphocytes
- would stain for Cytotoxic CD8+ Ts
- are invading muscle fibers (vs. dermatomyositis?)
26
Q
What is this sign?
A
Facial lipodystrophy in child w/ Juvenile Dermatomyositis
27
Q
Name this sign
A
calcinosis; can be seen in juvenile dermatomyositis
