Muscle Diseases Flashcards
How do muscle diseases present?
Muscle pain (myalgia), muscle weakness/tiredness, stiffness, abnormal blood tests, other organ features
What is a myopathy?
Disease of the muscle in which the muscle fibres don’t function properly, causing muscular weakness
What are polymyositis and dermatomyositis?
Idiopathic inflammatory myopathies
What are some features of inflammatory myopathies?
Autoimmune, twice as common in females, common in ages 40-50 years, increased incidence of malignancy
What are some clinical features of inflammatory myopathies?
Muscle weakness = insidious onset, worsening over months
Usually symmetrical, proximal muscles
Often specific problems (e.g climbing stairs)
Myalgia in 25-50% (usually mild)
What does dermatomyositis affect as well as muscles?
The skin = Gottron’s sign, heliotrope rash, shawl sign, purple/red rash
What are some common manifestations of inflammatory myopathies?
Interstitial lung disease, respiratory muscle weakness, dysphagia, myocarditis, fever, weight loss, Reynaud’s, inflammatory arthritis
What is the link between inflammatory myopathies and malignancy?
9% incidence in polymyositis, 15% incidence in dermatomyositis, greatest risk in men >45, ovarian, breast, stomach, lung, bladder and colon cancer
What are two methods of testing muscle strength?
Confrontational testing = direct testing of power
Isotonic testing = 30 second sit to stand test
What blood tests can be done to investigate inflammatory myopathies?
Muscle enzymes (CK), inflammatory markers, electrolytes, calcium, PTH, TSH (to exclude other causes)
What auto-antibodies may be present in inflammatory myopathies?
ANA, anti-Jo-1, myositis specific antibodies
What would an electromyography of inflammatory myopathies show?
Increased fibrillation, abnormal motor potentials, complex repetitive discharges
What would a muscle biopsy show for inflammatory myopathies?
Periarticular inflammation and muscle necrosis (definitive test for diagnosis)
What would be some MRI findings for a patient with an inflammatory myopathy?
Muscle inflammation, oedema, fibrosis, calcification
How should inflammatory myopathies be treated?
Corticosteroids
Immunosuppression = azathioprine, methotrexate, ciclosporin, rituximab, IV immunoglobulin
What is the epidemiology of polymyalgia rheumatica?
Occurs almost exclusively in those >50 years old, incidence higher in northern regions
What is polymyalgia rheumatica associated with?
Temporal/giant cell arteries
How does polymyalgia rheumatic manifest clinically?
Ache in shoulder and hip girdle Morning stiffness, usually symmetrical Fatigue, anorexia, weight loss and fever Reduced movement of shoulders, neck and hips Muscle strength is normal
How does granulomatous arteritis of large vessels present?
Headache, scalp tenderness, jaw claudication, visual loss (amaurosis fugax), tender enlarged non-pulsatile temporal arteries
What can be used to diagnose polymyalgia rheumatica?
ESR (raised), PV, CRP, temporal artery biopsy (best option), temporal artery USS
How should polymyalgia rheumatica be treated?
Rapid and dramatic response to low dose steroids, gradually reduce dose over 18months to 2 years, start at prednisolone 15mg daily
How should granulomatous arteritis be treated?
Start at 40-60mg of prednisolone daily
What is fibromyalgia the most common cause of?
Chronic MSK pain, especially in women aged 22-50
What are some associations of fibromyalgia?
Not associated with inflammation, may begin after emotional or physical trauma, linked to IBS, more common in women (6:1)
