Muscle Disease Flashcards
What are the two most common inflammatory myopathies?
When is the peak incidence of these?
What are these patients at higher risk of?
Polymyositis and Dermatomyositis
40-50 years
Increased risk of malignancy
What does histology show in Polymyositis and Dermatomyositis?
Features on muscle biopsy include muscle fibre necrosis, degeneration, regeneration and an inflammatory cell infiltrate –> the muscle itself is abnormal
What are the clinical features of Polymyositis and Dermatomyositis?
Muscle weakness – the most common presenting feature
Insidious onset, worsening over months
Usually symmetrical, proximal muscles of limbs
Often specific problems e.g. difficulty brushing hair, climbing stairs
Myalgia in 25-50% (usually mild)
Proximal muscles are typically affected – drying hair, hanging out washing, climbing up stairs, getting out of a chair
Describe the following signs: Gottrons sign Helitrope rash Shawl sign What condition are they typically associated with?
They are all erythmatous rashes associated with dermatomyositis:
Gottrons sign occurs on the dorsal aspect of hands
helitrope rash occurs in the eye areas of the face
Shawl sign occurs on the upper back
What other organs are involved in Polymyositis and Dermatomyositis?
Lung: Interstitial lung disease (10%); respiratory muscle weakness
Oesophageal: Dysphagia
Cardiac: Myocarditis
Other: Fever, weight loss, Raynauds phenomenon, non-erosive polyarthritis
Patients of what age and with what disease are actively screened for malignancy?
Risk greatest in men over 45 years – these patients are thoroughly screened for malignancy
What questions are important to ask in a patient with polymyositis or dermatomyositis?
Presenting symptoms : tired muscles, functional difficulty, muscle pain
Other medical problems : DM, hypothyroid disease
Drugs: particularly steroids, statins, don’t forget illicit drug use
Family history – e.g. muscular dystrophy (this is not inflammatory but important to ask about)
Social : alcohol, illicit drug use
Other symptoms : weight loss, cough, breathlessness, Raynauds
What would you do when examining a patient with suspected polymyositis or dermatomyositis?
Evidence for loss of muscle bulk
Confrontational testing - ask them to hold out their arms and then you press down on them to see if they can hold them up; this is a direct testing of power
Isotonic testing – ask them to repeatedly sit and stand up
What blood tests would you run in a patient with suspected polymyositis or dermatomyositis?
Muscle enzymes e.g. creatine kinase (CK)
Inflammatory markers
Electrolytes, calcium, PTH, TSH (to exclude other causes)
Autoantibodies: ANA, Anti-Jo-1 (specific for polymyositis and dermatomyositis)
What other investigations can you do in a patient with suspected polymyositis or dermatomyositis?
Electromyography (EMG): two needles are stuck into the skin and a current passed between them, giving increased fibrillations, abnormal motor potentials, complex repetitive discharges
Muscle biopsy: definitive test; perivascular inflammation and muscle necrosis
MRI: muscle inflammation, oedema, fibrosis and calcification
What is the definitive test for polymyositis and dermatomyositis?
Muscle biopsy
What are some options for treatment of polymyositis and dermatomyositis?
Glucocorticoids
Azathioprine
Methotrexate
Ciclosporin
IV immunoglobulin – used more by dermatology for skin disease
Rituximab – B cells depleting drug use in rheumatoid arthritis, can be very useful
Inclusion Body Myositis
What is this commonly mistaken for?
Features?
Investigations and their results?
Commonly mistaken for polymyositis, however it doesn’t respond well to treatment.
Features
- Patients >50 years, commoner in men (M:F, 3:1)
- More insidious onset
- Distal muscle weakness
- Weakness in wrist and finger flexors in upper limbs and quadriceps and anterior tibial muscles in legs
Weakness often asymmetrical
Investigation
- CK levels lower than in polymyositis
- Muscle biopsy shows inclusion bodies
- Responds poorly to therapy
Polymyalgia rheumatica (PR)
What age group
Where is incidence higher?
Whatt is it associated with?
Occurs almost exclusively in those over 50 years
Incidence higher in northern regions
Associated with temporal arteritis/giant cell arteritis (15%)
What are some common clinical manifestations of PR?
Ache/pain in shoulder and hip girdle
Morning stiffness – need help getting out of bed and then by the afternoon they’re relatively fine; once the stiffness has worn off, functionally they are able to do most things
Usually symmetrical
If you ask the patient to do a movement; it may be hard, but if you get them to relax and you do it for them, it should be fine (muscle strength is normal)
Fatigue, anorexia, weight loss and fever may occur
Reduced movement of shoulders, neck and hips
Muscle strength is normal
