Polymyositis Flashcards
What?
Idiopathic inflammatory myopathy
Pathophysiology?
T-cell mediated cytotoxic process directed against unidentified muscle antigens
CD8 T cells along with macrophages, initally surround healthy non- necrotic muscle fibres and eventuallty invade and destroy them
Serum antibodies?
Shared with other AI diseases = ANA, anti- RNP
Unique to myositis = anti- Jo-1, anti- SRP antibodies
Presentation?
Symmetrical proximal muscle weakness in upper & lower extremeties
Describe the onset of muscle weakness?
Insidious
Other clinical features?
Myalgia Dysphagia Interstitial lung disease Myocarditis Fever, weight loss, raynauds, inflammatory arthritis
Examination?
Look at muscles -> wasting?
Skin involvement> - for dermatomyositis
Test muscle power – confrontational testing, isotonic testing
Investigations?
Raised inflammatory markers Raised serum CK Autoantibodies MRI EMG Muscle biopsy
What does MRI show?
Show signal intensity abnormalities of muscle due to inflammation, oedema, scarring
What is the definitive diagnostic test?
Muscle biopsy
What does muscle biopsy show?
Muscle fibers in varying stages of inflammation, necrosis and regeneration
Management?
Prednisolone (40 mg) Immunosuppressive drugs (methotrexate or azathioprine)
Prognosis?
Responds to treatment (slowly)
Some residual weakness
Late presentation & older patients do worse
Who?
Women> men
45-60
