Myositis Flashcards

1
Q

Myositis classification

A

Adult onset DM: DM, Amyotrophic DM
Adult onset PM
Overlap myositis: ASA, Myositis assoc’d w/ CTD
Immune mediated necrotizing
IBM
Juvenile onset
Other: focal, giant cell, assoc’d w/ eosinophilia

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2
Q

**PM/DM diagnostic criteria **

A

Weakness
- Proximal painless weakness (no ocular/facial),
- Neck flexor weaker than extensor
- Pharyngeal (dysphonia),
- Upper esophageal (dysphagia)

  • Characteristic rash (Heliotrope, Gotton’s)
  • Elevated CK, aldolase, myoglobin, AST, ALT, LDH
  • MSAs/MAAs: Jo1
  • Abnormal EMG
  • Muscle biopsy
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3
Q

DM rash biopsy*

A

Interface dermatitis with mucin (similar to SLE)

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4
Q

** IIM EMG**

A
  1. Increased insertional activity w/ SPONTANEOUS FIBRILLATION and complex repetitive discharge
  2. LOW AMPLITUDE and SHORT DURATION POLYPHASIC motor unit action potential. EARLY RECRUITMENT
  3. Positive SHARP waves (initial down spike then wide up wave)
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5
Q

** DM Derm Manifestations & where **

A

Heliotrope (eyelid, malar, forehead, nasolabial)
-V sign (chest/neck)
-Shawl sign (shoulders, prox arms)
-Holster sign (lat thigh)
-Gottrons (dorsal MCP/IP, extensor wrist elbow, knee)
- Mechanic’s hands - thickened crackened skin on dorsal/ventral surfaces of hands

-Nailfold: periungal erythema, cuticular overgrowth, dilated capillary loops
-Photosensitivity

-Subcutaneous calcification (JDM)

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6
Q

DM mimics

A

Trichinosis
-Allergic contact dermatitis
-Drug reactions (hydroxyurea, pencillamine, diclofenac, anti TNF)

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7
Q

Biopsy tips to max yield

A

MRI to direct

-Biopsy weak muscle opposite to that of EMG

-Do not biopsy muscle within 2-4weeks of EMG or within 3 mo of rhabdo

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8
Q

Adult onset DM clinical features

A

Rash (NO mechanic hands)
-Muscle disease (20% amyotrophic)
-MSA

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9
Q

** DM muscle biopsy pathology **

A

COMPLEMENT mediated (vs T cell mediated in PM): C5b-9 MAC found on cells

-Perimysial and/or PERIVASCULAR inflamm (VASCULATURE = primary target vs endomysial myocyte in PM)

-PERIFASCICULAR ATROPHY of muscle fibers

  • Endomysial infiltration of mononuclear cells but NOT INVADING myofibers
  • B cells, pDC, and CD4+ NOT CD8 like in PM
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10
Q

DM MSA’s and characteristics*

A

Mi-2 - rash, periungal/cuticle growth, weakness. NO CANCER OR ILD, good prognosis. ANA+

-SAE - rash, myositis, DYSPHAGIA, ILD; CANCER

-MDA5 - ULCERATION (nailfold, over joints, oral), palmar papules, arthritis, fever, RAPID ILD, often AMYOPATHIC, ANA negative, NO CANCER

-Tif1Gamma - rash, low titre ANA, CANCER

-NXP2 - rash, fingertip ulcers, JDM,subcutaneous calcification, CANCER

-*all can have CADM except MI-2

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11
Q

Antisynthetase (ASA) characteristics

A
  • Proximal muscle weakness w/ elevated CK (5-10x ULN)
  • Raynauds
  • Mechanic’s hands (+/- Heliotrop/gottron)
  • ILD
  • Arthritis
  • Fever
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12
Q

Antisynthetase (ASA) muscle pathology

A

Similarto DM but WITHOUT complement deposition

Perimysial pathology +/- perifasciular atrophy

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13
Q

Myositis assoc w/ CTD
-Which CTD and MAA

A

SSc: PM-SCl, RNP, Ku, U3RNP
-MCTD/SLE (RNP)
-Sjogrens (Ro)

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14
Q

ASA MSA’s and assoc’d manifestations

A

*all have myositis and ILD

Jo1: rash, seroneg arthritis, Raynaud, fever, negative cancer association
-PL7: ILD> myositis, mechanic hand, arthritis, Raynaud, esophageal
-PL12: ILD > myositis, Raynaud, pHTN
-EJ: rash,
-OJ: rash, arthritis, fever

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15
Q

Adult onset PM clinical features

A

Prox muscle weakness w/ elevated CK without other cause
-Cardiac (conduction, CHF)
-Increased cancer risk

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16
Q

** PM muscle histology **

A
  • Endomysial > perimysial inflammation (CD8+ T cells)
  • Endomysial infiltrates invade NON-NECROTIC fibers
  • MHC class 1 on sarcolemma
  • Vasculature SPARED
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17
Q

** Cancers assoc’d w/ DM/PM **

A

Adenocarcinoma:
- Breast, Ovary
- Lung
- GI: pancreas, stomach, colon,
- Taiwanese (nasopharyngeal and cervical)

-Hematologic: hematopoeitic cancer, and Hodgkin’s

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18
Q

** High risk for Cancer in IIM**

A

-Dermatomyositis
-TIF1γ
-NXP2
->40yo at IIM onset
-Persistent high dz activity despite tx (including relapse of previously controlled disease)
-Dysphagia (moderate to severe)
-Cutaneous necrosis or ulceration

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19
Q

Intermed Risk factors for Cancer in IIM

A

-Male sex
-IMNM: Anti-HMGCR
-PM: Anti-Mi2, SAE
-Anti-MDA5, CADM

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20
Q

Immune-mediated necrotizing myopathy (IMNM) clinical characteristics

A

-Myositis (prox weakness)
-MYALGIA
-HIGH CK 10-50xULN, rhabdo
-NO ILD/rash
-Rare assoc w cancer, HIV, ASA, another CTD
-Can be REFRACTORY to tx, bad prognosis

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21
Q

** Immune-mediated necrotizing myopathy (IMNM) muscle histology **

A

-Necrotic fibers
-Macrophage INVASION
-MINIMAL CD8+ T cells or lymphocyte infiltrate

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22
Q

Immune-mediated necrotizing myopathy (IMNM) MSA and manifestations*

A

BOTH have severe myositis
NEITHER have ILD, rash

-SRP - PAIN (necrosis), myocarditis, dysphagia. ANA neg

-HMGCR (aka 200/100) - Statin exposure (lovastatin, simvastatin) or cancer or red yeast rice or oyster/shitake mushroom.
DRB1*11:01 HLA

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23
Q

** IBM vs PM **
Demographic
Muscle involvement
Other organs
ANA
MSA
EMG
Response to therapy

A
  • MC IIM >50
  • SLOW onset
    -Proximal AND DISTAL muscle (Knee/foot extensor, finger flexor); Asymmetric
    -NO RASH, ILD, CANCER
    -Other organs: neuropathy (vs ILD, arthritis, cardiac in PM)
    -No MSA; sometimes ANA, C1NA
    -EMG: myopathic and neuropathic
    -POOR RESPONSE Tx
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24
Q

** IBM muscle biopsy histology pathology**

A

Similar to PM
-CD8+ T cell infiltrate
- No perifascicular atrophy
- MHC class 1 expressed

Unique:
-Rimmed vacuoles
-Ragged red fibers
-Amyloid deposits
-Eosinophilic cytoplasmic inclusion

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25
Q

IIM DDx

A

Drug/Toxin: statin, interferon alpha, colchicine, amiodarone, antimalarias, AZT, alcohol, GC, cocaine, antifungal, anti TNF

-Neuromuscular: muscular dystrophy, NMJ d/o (MG, ELS), Denervating (ALS)

-Endocrine: hypo/hyperTSH, acromegaly, cushing, addison
-Infectious: bacterial (staph, strep, borrelia), viral (HIV, adenovirus, influenza), parasitic (toxo, trichinella, taenia)

-Metabolic: Glycogen storage, abN lipid metabolism, mitochondrial myopathy, nutritional d/o (vit D/E), electrolyte d/o (hypoCa/Ca/K/PO4)

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26
Q

DM/PM Poor prognostic features

A

-Severe weakness
-Dysphagia
-Respiratory muscle involvement
-ILD
-Myocardial involvement
-Cancer
-MDA5
-Pathology: necrotizing myopathy

27
Q

** Myositis Tx - nonpharm and pharm **

A

Pred 1-1.5mg/kg (up to 80mg/d) divided dose until remission (normal CK and strength ~4-6wk) - taper 20% monthly until 20mg, then 5mg monthly until 10mg x3-6mo before taper

-MTX 25mg/wk
-AZA 2-3mg/kg/d
-MMF 1-1.5g BID (ILD/rash)
-LFN
-CYC only if severe (eg MDA5 ILD) and JDM w/ vasculitis

-Tacrolimus 0.1mg/kg/kd; 2-5mg BID if resistant T cell mediated PM and lung dz
-Cyclosporine 3-5mg/kg/d

-IVIG 2g/kg x5d → monthly 2g/kg over 3d for severe refractory DM (esp dysphagia and HMGCR)

-RItux - 1g d1 and d15 → 1g q6mo

-Repository corticotropin injection - 80USP units SC twice a week x3 mo

-Nonpharm:
-rehab - passive/active assisted x4-6 weeks until strength and inflamm improves
-Vaccines
-OP
-PJP

28
Q

** Steroid myopathy vs IIM exacerbation **

A

Steroid myopathy
- NO elevated CK/aldolase,
- NO MRI inflammation
- Acute (eg ICU) - prox + distal
- Chronic - proximal - pelvic > arms
- Biopsy - nonspecific atrophy of type 2b fibers WITHOUT inflamm infiltrate

29
Q

** Risk factors for statin myopathy**

A

Statin characteristics: higher dose, lovastatin/simvastatin > others
-Other drugs inhibiting CYP3A4
-Other neuromuscular d/o: eg ALS
-Hypothyroidism
-Hypovitamin D

30
Q

** 3 drugs which increase risk of statin myopathy**

A

CYP3A4 inhibitors: cyclosporin, macrolides, azole antifungals, HIV/HCV protease inhibitors
-Competitive CYP3A4 binders: colchicine with simvastatin.
-Drugs that also cause myopathy (gemfibrozil)

31
Q

** Nonpharm contributor to statin myopathy **

A

Grapefruit consumption
-Strenuous exercises
-Hypothyroidism
-Vitamin D def (myalgia)

32
Q

** FIVE elements that indicate a non-inflammatory cause in myopathies**

A

Muscle involvement: proximal AND distal, facial
-No inflammation: normal CK, ESR, CRP, no inflamm infiltate on bx
-Trigger: Exercise
-Not responding to steroids
-FamHx or early childhood
-EMG not showing myopathic

33
Q

** Statin MSK manifestations**

A

Myalgia
-Asymptomatic hyperCK (neg MRI)
-Myositis
-Rhabdo (CK, myoglobinuria, AKI)

34
Q

** 5 ways you can distinguish adult myotonic dystrophy from an inflammatory myositis**

A

Muscular dystrophy vs IIM
– Genetic vs Inflammatory
– Childhood (mostly) vs Adult (mostly)
– Proximal and distal vs Proximal
– Steroid response: none vs responsive
– Cardiomyopathy: Often vs not often
– AB: none vs myositis AB
– Biopsy: low/no dystrophin staining vs perimysial/perivascular inflamm
– Genetic testing for muscular dystrophy

35
Q

Myositis antibody, name specific clinical finding: Jo1

A

MC AB for Antisynthetase
-PM/DM w/ ILD

36
Q

Myositis antibody, name specific clinical finding: PL7

A

Antisynthetase
-PM/DM w/ ILD
ILD> myositis, mechanic hand, arthritis, Raynaud, esophageal

-OJ:

37
Q

Myositis antibody, name specific clinical finding: PL12

A

Antisynthetase
-ILD more often than Myositis (clinically amyopathic)
-Raynaud
-pHTN

38
Q

Myositis antibody, name specific clinical finding: EJ

A

Antisynthetase
-PM>DM w/ ILD

39
Q

Myositis antibody, name specific clinical finding: OJ

A

Antisynthetase
-PM/DM w/ ILD
-Fever

40
Q

Myositis antibody, name specific clinical finding: KS

A

Antisynthetase
-ILD more often than Myositis

41
Q

Myositis antibody, name specific clinical finding: Zo

A

Antisynthetase
-ILD with Myositis

42
Q

Myositis antibody, name specific clinical finding: Ha

A

Antisynthetase
-ILD with Myositis

43
Q

Myositis antibody, name specific clinical finding: Mi2

A

DM w/ rash > muscle symptoms
-NO cancer or ILD
-Good prognosis (tx RESPONSIVE)
- ANA+

44
Q

Myositis antibody, name specific clinical finding: MDA5

A
  • DM (gottron, helitrope, shawl, V, holster)
  • **Often AMYOPATHIC, CADM **
  • Palmar papules
  • Polyarthritis, fever,
  • Alopecia
  • ULCERATION (nailfold, over joints, oral),
  • Less cancer but possible
    -DM w/ rapidly progressive ILD
    -Pneumomediastinum
  • ANA negative,
45
Q

Myositis antibody, name specific clinical finding: Tif1G

A

-DM
-Classic DM Rash
-Low titre ANA
-MOST associated with cancer

46
Q

Myositis antibody, name specific clinical finding: NXP2

A

DM - classic rash, finger tip ulcer,
-Subcutaneous calcification
-Juvenile DM
-Cancer associated

47
Q

Myositis antibody, name specific clinical finding: SAE

A
  • DM + mild ILD
    -Cancer associated
    -Dysphagia
48
Q

Myositis antibody, name specific clinical finding: SRP

A

Severe, acute, resistant necrotizing myopathy

49
Q

Myositis antibody, name specific clinical finding: HMG COA reductase

A

Necrotizing myopathy related to statin use in majority

50
Q

DDX ILD with skin features, and NO muscles weakness

A
  • SLE
  • Sjogren’s
  • ANCA vasculitis (especially MPO+)
  • DM - MDA5/CADM
  • DM - SAE (ILD is rare however)
  • Antisynthetase syndrome (often have weakness)
  • IPAF (interstitial PNA w/ autoimmune features)
51
Q

** Causes of necrotizing myositis**

A
  • Anti-SRP, HMGCR necrotizing myopathy (+/- statin exposure)
  • Antisynthetase syndrome w/ necrotizing myopathy
  • Cancer associated myositis
  • Viral necrotizing myopathy: HIV, HCV
  • Overlap syndrome necrotizing myopathy (SSc features/antibodies)
52
Q

** Antisynthetase AB’s and their target**

A

Jo1
PL2/7
EJ/OJ
KS
Zo
Ha

**target against amino-acyl t-RNA synthetase
(eg Jo1 against cytoplasmic protein histidyl tRNA synthetase 1)

53
Q

** Treatment for resistant skin dz in IIM**

A

Aggressive sun protection
Topical
Antipruritic
Antimalaria

Aza, MMF, MTX
Dapsone, IVIG, RTX, CNI
Tofa

54
Q

** Causes of high CK **

A

Transient: exercise, trauma, seizure, psychosis

Cardiac: MI, arrhytmia, myocarditis

Neurogenic: radiculopathy, motor neuron disease (ALS), mononeuritis multiplex

Myopathic - acquired:
- Drugs (statin, EtOH, cocaine, chloroquine, colchicine, statins)
-Endocrine (hypo/hyperthyroid, hypoPTH, hypoK/PO4),
-IIM (PM, DM, IMNM)
- Infection: viral/fungal myositis

Myopathic - Inherited:
- Muscular / myotonic dystrophies,
- Metabolic myopathies

55
Q

**Drugs causing muscle disease or elevated CK

A
  • Antidepressants: TCA, venlafaxine, sertraline, escitalopram
  • Antipsychotics: Seroquel, haldol, clozapine, olanzapine
  • Antiretrovirals: tenofovir, abicavir, ralegravir
  • Antimalarials
  • Daptomycin
  • Lithium
  • Colchicine
  • Statin
56
Q

**Enzymes elevated in IIM
-Which is most sensitive vs specific **

A

-CK = most sensitive and specific
-Aldolase,
-Myoglobin,
- AST, ALT,
- LDH

57
Q

** Extramuscular & extraderm Sx of DM/PM**

A

Constitutional symptoms

MSK
- Arthralgias,
- Arthritis (20-70%); associated with antisynthetase syndrome

Pulmonary:
- ILD (70% of patients with antisynthetase antibodies);
- Aspiration pneumonia;
- Respiratory muscle weakness,
- pHTN

GI:
- Esophageal dysmotility (10-30%);
- Reflux due to lower esophageal sphincter weakness (15-50%);
- Rectal incontinence due to sphincter ani weakness;
- Intestinal perforation due to vasculitis (more juvenile)

Cardiac:
- Arrhythmias,
- Conduction blocks,
- Myocarditis

Vascular:
- Raynaud’s (20-40%)
- Vasculitis (juvenile DM),
- Skin ulcerations (juvenile),
- Livedo reticularis,

58
Q

Hyperthyroid vs Hypothyroid CK levels

A

Normal in Hyperthyroid
Elevated in Hypothyroid

59
Q

** Components of NORMAL EMG (vs in myopathy) **

A

Insertional/spontaneous activity:
-should not have spontaneous activity (vs variable fibrillation and sharp waves in myopathy)

Motor unit analysis (amplitude, duration, # of phases, firing pattern)
- Morphology normal (vs small amplitude, short duration, increased polyphasia)

Recruitment - number of recruitable motor units
- Normal (vs early recruitment)

60
Q

** Indications to order EMG **

A

Localize pathology of neuromuscular disorder: neurogenic vs myopathic, vs NMJ

Determine severity of suspected neuromuscular disorder

61
Q

** How to tell neurogenic vs myopathic conditions apart on EMG **

A

Myopathic: EARLY recruitment = large number of motor units but SMALL amplitude, POLYphasic >4phases in a wave

Neurogenic: REDUCED recruitment bc axon/neuron loss but LARGE amplitudes

62
Q

** How to differentiate demyelinating peripheral neuropathy and an axonal peripheral neuropathy by NCS and EMG **

A

NCS:
- Demyelinating: SLOWED conduction velocities with PRESERVED compound muscle action potential (CMAP)/sensory nerve action potential (SNAP) amplitudes
- Axonal neuropathies have REDUCED CMAP/SNAP amplitudes with PRESERVED conduction velocities.

EMG:
- Axonal neuropathies have EARLY denervation abnormalities
- Demyelinating neuropathies show denervation abnormalities LATER when axons are secondarily affected

63
Q

3 similarities and 3 differences between the pathology for DM/PM

A

3 differences:
- Complement in DM (vs T-cell mediated in PM)
- Infiltrate CD4 predominant and other cells like B-cells, dendritic cells (DM) vs CD8 predominant (PM)
- Perivascular infiltrate (DM) vs endomysial infiltrate (PM)
- Perifascicular atrophy (DM) vs invasion of non-necrotic fibres (PM)

3 similarities:
- Upregulation of MHC1;
- Muscle fibre necrosis;
- Evidence of degeneration and regeneration