Muscle Diseases Flashcards
What are two endocrine conditions which can cause myopathy?
Hypothyroidism, Cushing’s
What common medication can cause myopathy?
Statins
What causes myositis?
No cause, idiopathic
Are polymyositis and dermatomyositis inflammatory conditions?
Yes
Which sex are polymyositis and dermatomyositis most common in and by how much?
Twice as common in women
What is the age of peak incidence of polymyositis and dermatomyositis?
45-60
What is the difference between polymyositis and dermatomyositis?
The same muscle disease, dermatomyositis causes cutaneous features
What should all patients diagnosed with poly/dermatomyositis be screened for?
Malignancy, these conditions increase risk
Who is dermatomyositis most likely to be a paraneoplastic syndrome in?
Males over 50
What mediates the process of myositis?
Cytotoxic T cells
What cells surround healthy non-necrotic muscle fibres but then eventually invade and destroy them in myositis?
CD8+ T cells and macrophages
What are 4 features of myositis on a biopsy?
- Muscle fibre necrosis - Degeneration - Regeneration - Inflammatory cell infiltrate
What is the main symptom of myositis?
Muscle weakness
Is the muscle weakness in myositis of sudden or gradual onset?
Gradual, worsening over months
Which of the following describes the muscle weakness in myositis? a) Symmetrical or Asymmetrical b) Proximal or Distal
Symmetrical and proximal
Which muscles are generally affected by myositis?
Hip and shoulder girdle
What do the symptoms of myositis relate to?
The functional weakness of the muscles, i.e. difficulty doing particular tasks
Do myositis patients get myalgia?
Mild, in some patients
What is Gottron’s Sign and when is it seen?
Papules over the joints in the hands- dermatomyositis
What are respiratory features of myositis?
ILD/pulmonary fibrosis (5-30% of patients), respiratory muscle weakness
What makes myositis patients more prone to ILD?
Being positive for anti-Jo-1
What GI symptom occurs in a third of myositis patients? What does its presence indicate?
Dysphagia- a poor prognostic sign
What cardiac feature can myositis cause?
Myocarditis
What are some general symptoms of myositis?
Fever, weight loss, Raynaud’s, non-erosive polyarthritis
Which has a higher risk of malignancy, polymyositis or dermatomyositis?
Dermatomyositis (15%) (As opposed to polymyositis at 9%)
What are the cancers which myositis predisposes to?
Ovarian, breast, lung, stomach, oesophageal, bladder, colon
What age/sex is the risk of malignancy in myositis highest?
Males > 45
What % of myositis patients have an increased risk of malignancy? When is this risk highest?
25%- highest in the first 5 years following diagnosis
What past medical history may be of relevance in myositis?
Diabetes, thyroid disease
What drugs may be of relevance in myositis?
Steroids, statins
What is an example of isotonic testing used for myositis?
Sit to stand test- how many times can they do this in 30 seconds
What are you looking for in blood tests for myositis?
- Raised CK (sometimes by 10x) - Raised inflammatory markers - Also check electrolytes, Ca++, PTH, TSH
What is the main antibody which is specific for myositis?
Anti-Jo-1
Auto-antibodies are detected in how many patients with myositis?
60-80%
What other antibody is found in myositis which is sensitive but not specific?
ANA
What is another antibody which is said to be specific for myositis?
Anti-SRP
What is an electromyography?
A fine needle is inserted into 2 areas of muscle and a low electric current is passed through to see if it conducts or not
What is the definitive, gold standard test for myositis?
Muscle biopsy
Is a muscle biopsy the same for poly and dermatomyositis?
No, they have different patterns
MRI can be used for myositis to assess the degree of muscle involvement. What are some things it can show?
- Inflammation - Oedema - Fibrosis - Calcification
What is the main treatment for myositis?
Start with a high dose of prednisone and then reduce the dose. To reduce the amount of steroids, start an immunosuppressant such as methotrexate or azathioprine but make sure the steroid is on until these have time to work.
Will patients with myositis be on immunosuppressants lifelong?
Yes
What should be used if myositis patients don’t respond to immunosuppressants?
IV immunoglobulin Rituximab
What % of myositis patients are left with residual muscle weakness even after treatment?
Around 30%
Which groups of myositis patients do not respond as well to treatment?
Older people and those who presented late
What is a problem which can commonly be misdiagnosed as polymyositis?
Inclusion body myositis
Who does inclusion body myositis occur in? Which sex is most common?
Patients > 50, more common in men
How is inclusion body myositis different in terms of symptom onset than polymyositis?
More insidious onset than polymyositis
Which muscles does inclusion body myositis affect?
Distal muscles (wrist and finger flexors, quadriceps and anterior tibial muscles)
Is the weakness in inclusion body myositis symmetrical or asymmetrical?
Asymmetrical
Is inclusion body myositis an inflammatory condition?
Yes, but not to the degree of polymyositis
Is inclusion body myositis an autoimmune condition?
No
What will CK levels be in inclusion body myositis?
Raised, but not as much as in polymyositis
What will a muscle biopsy show in inclusion body myositis?
Inclusion bodies
Does inclusion body myositis respond to treatment?
No
When is this rash seen?
It continues at the back, what is this known as?
Dermatomyositis
Shawl sign
When is this sign seen?
What is it known as?
Dermatomyositis
Gottron’s Sign
When is this rash seen?
What is it known as?
Dermatomyositis
Heliotrope rash
Is polymyalgia rheumatica inflammatory?
Yes
What is the cause of polymyalgia rheumatica?
Uknown
Who does polymyalgia rheumatic occur in?
Almost exclusively the over 50s
Polymyalgia rheumatica has a higher incidence where?
Northern countries
What other condition is polymyalgia rheumatica assicated with?
Describe this association.
Giant cell arteritis
15% of patients with PMR have GCA
40-50% of patients with GCA have PMR
What is polymyalgia rheumatic characterised by?
Muscle pain and stiffness
Where are the symptoms of polymyalgia rheumatica usually?
Are they symmetrical or asymmetrical?
Shoulder and hip girdle
Symmetrical
Describe the morning stiffness experienced in polymyalgia rheumatica?
Can last up to a few hours and then gets better- improves with movement
What are some general features of polymyalgia rheumatica, which can also be caused by GCA?
Fatigue, anorexia, weight loss and fever
What are some symptoms of GCA?
Headache, scalp tenderness, jaw claudication, tender and pulsatile arteries, vision changes
Vision loss is permanent in what % of patients with GCA?
20%
Why does vision loss occur in GCA?
The temporal artery supplies the optic nerve
How do you diagnose polymyalgia rheumatica?
Exclude other diagnoses
Raised inflammatory markers
What test should be done ASAP if there are signs of GCA?
Temporal artery biopsy
Will polymyalgia rheumatica show a change on muscle biopsy?
No
How long will polymyalgia rheumatica last for?
18 months - 2 years
What aspect of treatment for polymyalgia rheumatica can actually be used as a diagnostic test?
It has a very rapid and dramatic response to treatment with low dose steroids
Is the dose of prednisolone kept the same through the whole time a patient has polymyalgia rheumatic/GCA?
No, it is tapered down
What is the normal starting dose of prednisolone for polymyalgia rheumatica?
15mg
What dose of prednisolone should be given for polymyalgia rheumatica with a headache and no visual changes?
40mg
What dose of prednisolone should be given for polymyalgia rheumatica with vision changes?
60mg
When should you start treatment with high dose prednisolone when there is suspected GCA?
Straight away- do not wait for the results of a biopsy
GCA involves transmural inflammation of where?
The tunica intima, media and adventitia of affected arteries
GCA involves infiltration by what cells?
Lymphocytes, macrophages and multinucleated giant cells
Vessel wall thickening in GCA causes lumen narrowing which results in what?
Distal ischaemia, particularly of the temporal artery
How might the temporal artery look in GCA?
Thickened, prominent and tender to touch
When should GCA always be considered as a differential diagnosis?
New-onset headahce in over 50s with raised inflammatory markers
Describe the headache of GCA and where is it located?
Continuous and located in the temporal/occipital areas
What is jaw claudication? What causes it?
Fatigue or discomfort of the jaw muscles during chewing or prolonged speaking
Caused by ischaemia of the maxillary artery
What is the most definitive test for GCA?
Temporal artery biopsy
What is the sensitivity and specificity of a temporal artery biopsy?
100% specificity
15-40% sensitivity
Why does a temporal artery biopsy have a low sensitivity for GCA?
There is only patchy involvement of the artery i.e. some segments may be normal
Is fibromyalgia inflammatory?
No
What does fibromyalgia cause?
Widespread muscle pain and fatigue
Who does fibromyalgia occur in?
Mostly in young and middle aged women but can affect anyone
The cause of fibromyalgia is unknown. What are some potential triggers?
Emotional or physical trauma
Poor sleep pattern (can predate the onset of pain)
Fibromyalgia patients tend to have a low threshold to what things?
Pain, heat, noise and strong odours
What is the theory behind the pain of fibromyalgia?
Abnormal pain signalling as the pathways become oversensitive
Is fibromyalgia a primary or secondary condition or both?
Can be primary or secondary (common links with RA and SLE)
What are thmain features of fibromyalgia?
Persistent (3+ months) of widespread pain
Fatigue and poor, unrefreshing sleep
Cognitive difficulties
Anxiety, depression, impaired activities of daily living
What effect does exercise have on fibromyalgia pain?
Makes it worse
What other conditions can fibromyalgia be associated with?
Depression, migraines, IBS
How do you diagnose fibromyalgia?
Normal inflammatory markers and exclusion of other causes
What are the main management options for fibromyalgia?
Self-management and understanding of the condition
Advice about graded exercise and activity pacing
CBT
Complementary medicines
Physio/occupational therapy
If medications are going to be used for fibromyalgia, what will be used?
Amitriptylline, gapapentin, pregabalin
