Polymyositosis Flashcards
what type of myopathy is polymyositosis
idiopathic inflammatory
what type of muscle weakness is seen
symmetrical and proximal
is it more common in women or men
women 2:1
what is the typical age of onset
20 and over especially 45-60 year olds
what is the immunology behind this
T cell mediated cytotoxic process directed against unidentified muscle antigens
CD8 T cells along with macrophages initially surround healthy nonnectrotic muscle fibres and eventually invade and destroy them
what percentage of patients have an autoimmune response to nuclear and cytoplasmic autoantigens
60-80%
what are some of the serum autoantibodies found in polymyositis that are shared with other autoimmune diseases
ANA and anti-RNP antibody
what are some of the serum autoantibodies that are unique to polymyositis
anti-Jo-1 and anti-SRP antibodies
how do patients with polymyositis usually present
symmetrical and proximal weakness in upper and lower extremities of insidious onset commonly noticed as difficulties with particular activities
some patients have myalgia
what are some of the activities polymyositis is noticed with
climbing stairs
what can dysphagia occur due to
secondary to oropharyngeal and oesophageal involvement
what percentage of patients with polymyositis present with dysphagia
33%
poor prognostic sign
what percentage present with interstitial lung disease
5-30%
what patients are more likely to present with ILD
positive for anti-Jo-1
what investigations are done
raised inflammatory markers
creatine kinase raised 10 times the normal level
antibodies including ANA, anti-Jo-1 and anti-SRP, MRI, electromyography, muscle biopsy is crucial
what is MRI useful for
localise the extent of muscle involvement
what percentage of parents that have abnormal electromyography
90%
what does muscle biopsy show
muscle fibres in varying stages of inflammation, necrosis and regeneration
what is the management
prednisolone (40mg) combined with immunosuppression drugs (methotrexate or azathioprine)
how well does polymyositis respond to treatment
well but slowly, 30% have residual weakness, older patients tend too do less well
