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MBChB YR2 MSK > Disease Profiles: Muscle Diseases > Flashcards

Disease Profiles: Muscle Diseases Flashcards

(65 cards)

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1
Q

What is myasthenia gravis?

A

Severe autoimmune neuromuscular disorder characterised by severe muscular weakness and progressive fatigue

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2
Q

What is MRI used for in suspected polymyositis or dermatomyositis?

A

Used to localise the extent of muscle involvement

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3
Q

Which patient group is most likely to develop myasthenia gravis?

A

Can occur at any age but usually presents at after middle age - most commonly 60-70

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4
Q

Which type of hypersensitivity is myasthenia gravis associated with?

A

Type II

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5
Q

What causes polymyositis and dermatomyositis?

A

CD8+ T cell mediated reaction against muscle antigens

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6
Q

Describe the management of tetanus

A

Surgical debridement, anti-toxin, supportive measures (e.g. benzodiasapines, beta blockers), 7-10 days antibiotics, booster vaccination

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7
Q

Name the two inflammatory myopathies

A

Polymyositis and dermatomyositis

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8
Q

Describe the non-pharmacological management of fibromyalgia

A

Education, graded exercise, CBT, complementary medicine e.g. acupuncture

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9
Q

Describe MRI changes seen in polymyositis or dermatomyositis

A

Muscle inflammation, oedema, fibrosis and calcification

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10
Q

What is polymyositis?

A

Idiopathic inflammatory myopathy that causes symmetrical, proximal muscle weakness

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11
Q

What is usually the first line treatment for myasthenia gravis (if not associated with a thymic tumour)?

A

Anticholinesterases

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12
Q

What is usually the second line treatment for myasthenia gravis (if not associated with a thymic tumour)?

A

Immunosuppressive drugs, corticosteriods

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13
Q

Which bacteria is associated with pyomyositis in contaminated wounds?

A

Clostridium

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14
Q

What are the antibodies associated with polymyositis and dermatomyositis?

A

Non-specific - ANA, anti-RNP

Myositis specific - Anti-Jo-1, anti-SRP

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15
Q

Name the enzymes normally raised in patients with polymyositis or dermatomyositis

A

Muscle enzymes e.g. creatine kinase

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16
Q

What is the definitive test for polymyositis or dermatomyositis?

A

Muscle biopsy

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17
Q

Describe the pathophysiology of myasthenia gravis

A

anti-AChR antibodies are generated in response to AChR subunits expressed by thymic myoid cells (via CD4+ TH cells and B cells)

The anti-AChR antibodies block the binding of ACh to the ACh receptors at the neuromuscular endplate

Endplate potential is not sufficient to trigger muscular contraction

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18
Q

Name a complication of polymyositis and dermatomyositis and name which patient group is most at risk

A

Increased risk of malignancy

Greatest risk in males > 45 years

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19
Q

Which is the most common causative organism for pyomyositis?

A

Staphlococci (90%)

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20
Q

Describe how tetanus can be prevented

A

Routine vaccination, good wound management

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21
Q

Describe the clinical presentation of polymyositis and dermatomyositis

A

Symmetrical, proximal muscle weakness in the upper and lower extremities, insidious onset and gets worse over months

Myalgia in 25-50%

Muscle wasting

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22
Q

Describe a positive muscle biopsy for polymyositis or dermatomyositis

A

Perivascular inflammation and muscle necrosis

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23
Q

What causes myasthenia gravis?

A

Autoimmune disorder - 90% idiopathic, 10% due to thymic tumour

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24
Q

Which patient group does polymyositis and dermatomyositis most commonly occur in?

A

Females age 40-50 years

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25
What is pyomyositis?
Acute intramuscular infection secondary to haematogenous spread of the microorganism into the body of a skeletal muscle, most commonly caused by Staph. aureus
26
Name the gene complex associated with a genetic predisposition for myasthenia gravis
HLA associations
27
Describe the pathophysiology of fibromyalgia
Thought to be a disorder of central pain processing or a syndrome of central sensitivity - patients have lower threshold for pain and other stimuli e.g. heat Can begin after trauma (emotional or physical)
28
What is dermatomyositis?
Idiopathic inflammatory myopathy that causes symmetrical, proximal muscle weakness, and cutaneous manifestations
29
Which organism is associated with myonecrosis?
Clostridium perfringens
30
What does imaging (x-ray, CT or MRI) typically show in myonecrosis?
Feathering pattern of soft tissue
31
Describe the management of myonecrosis
Immediate surgical debridement and antibiotic therapy
32
Describe the clinical presentation of fibromyalgia
Persistent (≥ 3 months) widespread pain on both sides of the body, above and below the waist, includes the axial spine and chest pain (non-cardiac) Fatigue - disrupted and unrefreshing sleep Headaches, cognitive and memory impairment, anxiety and depression
33
Describe the clinical presentation of pyomyositis
Pain and swelling of the affected area (usually lower extremities), fever
34
Name two conditions which have been associated with fibromyalgia
RA, SLE
35
Which investigation would you perform in suspected tetanus?
Wound culture
36
What would you expect to see in a wound culture from a patient with tetanus?
Anaerobic gram positive with terminal spore
37
Name three cutaneous features of dermatomyositis
Gottron's sign, heliotrope rash, shawl sign
38
What is the mechanism of action of anticholinesterases for myasthenia gravis?
Increase neurotransmission by increasing the concentration of ACh in the synaptic cleft
39
How would you diagnose fibromyalgia?
Diagnosis of exclusion - patient experiences widespread pain and associated symptoms, symptoms at the same level for ≳3 months and there is no other explanation
40
Which antibody is associated with the development of interstitial lung disease in patients with polymyositis or dermatomyositis?
Anti-Jo-1
41
What is tetanus?
Acute disease caused by neurotoxins from the bacterium Clostridium tetani
42
When is a thymectomy indicated in myasthenia gravis?
When MG is associated with a thymic tumour - first line if indicated
43
Describe possible electromyography findings in patients with polymyositis or dermatomyositis
Increased fibrillations, abnormal motor potentials, complex repetitive charges
44
What is fibromyalgia?
Neurosensory disorder characterised by chronic MSK pain
45
Describe the clinical presentation of myonecrosis
Disproportionate muscle pain, massive edema with skin discoloration May be no fever or cutaneous manifestations but can rapidly progress to systemic infection (within hours)
46
What is viral myositis?
Muscle inflammation due to a viral infection e.g. influenza, enteroviruses, HIV, HTLV, CMV, rabies, dengue
47
Which patient group is most likely to develop fibromyalgia?
Commonest cause of MSK pain in women 22-50
48
Describe the clinical presentation of tetanus
Trismus (lock jaw), risus sardonicus, autonomic instability
49
Which bacteria are associated with pyomyositis in immunosuppressed patients?
Psudomonas, beta haemolytic strep. enterococcus
50
Which class of bacteria is associated with pyomyositis in the perineum?
Gram-negative bacteria
51
Describe the clinical presentation of viral myositis
Muscle pain, tenderness, swelling and often weakness, typically after a few days of fever
52
Which investigations would you perform in suspected myonecrosis?
X-ray, CT or MRI Lab tests - Gram staining, wound culture, blood culture
53
What two examination tests would you perform in suspected polymyositis and dermatomyositis?
Confrontational testing (of power) 30 second sit to stand test
54
Define myopathy
Disease of the muscle in which the muscle fibres do not function properly
55
Describe the management of viral myositis
Symptomatic
56
How would you manage patients with polymyositis or dermatomyositis?
Prednisolone treatment of choice - aim to gradually lower dose, eventually stop Alternative treatments if not responsive: immunosuppression e.g. azathioprine, methotrexate, IV immunoglobin, rituzimab
57
Describe the management of pyomyositis
Antibiotics and surgery (debridement)
58
Which investigations would you perform for suspected myasthenia gravis?
Lab tests - anti-AChR IgG in serum Repetitive nerve stimulation - gradually reducing responses indicates NMJ dysfunction
59
Why can myasthenia gravis be life-threatening?
In advanced stage all muscles are weak → life-threatening impairment of respiration
60
Describe the pathophysiology of tetanus
C. tetani spores found in soil, enter the body through broken skin After incubation (4 days to several weeks) the toxin binds to inhibitory neurons, preventing release of inhibitory neurotransmitters → widespread activation of motor neurons and spasming of muscles throughout the body
61
Describe the clinical presentation of myasthenia gravis
Insidious onset of fatigue and progressive muscle weakness Muscles of the eyes, mouth, throat and neck usually affected first
62
Which bacteria is associated with pyomyositis in tropical climates?
MSSA infection in immune competant patients and children
63
Which investigation would you perform in suspected viral myositis?
Bloods - elevated CK
64
What is myonecrosis?
Life-threatening necrotizing soft tissue infection commonly caused by the rapid proliferation and spread of Clostridium perfringens from a contaminated wound
65
Describe the pharmacological management of fibromyalgia
Anti-depressants e.g. tricyclics, SSRIs Atypical analgesia including tricyclics (e.g. amitriptyline), gabapentin and pregabalin

MBChB YR2 MSK (36 decks)

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