Idiopathic inflammatory myopathies (IIMs) are a heterogeneous group of
myositis, characterised by chronic
muscle weakness, cutaneous features, different extra-muscular manifestations and circulating
autoantibodies. IIMs included classical
polymyositis (PM),
dermatomyositis (DM) and other different types of
myositis with a wide range of muscle involvement. A complete
autoantibody profile and a muscle biopsy are mandatory to correctly diagnose different clinical entities and to define their different prognosis. Bohan and Peter's criteria included five items to diagnose adult onset PM and DM. The sensitivity was 74-100 %, while the specificity is low, due to a poor ability to differentiate PM from
neuromuscular diseases. Other criteria included a more accurate histological definition of PM, DM or amyopathic DM, obtaining a higher specificity.
Autoantibodies' association,
interstitial lung disease and clinical cardiac involvement represent the main items that could define the prognosis of these patients. On the other hand,
inclusion body myositis is a different
myopathy characterised by a peculiar muscle mass involvement,
muscle atrophy and progressive loss of function, due to complete failure to all immunosuppressive drugs used. Treatment of IIMs is based on
corticosteroids (CS), which show rapid clinical response and functional improvement. Different
immunosuppressant drugs are given to obtain a better control of the disease during CS
tapering dose. No controlled double blind trials demonstrated the superiority of one immunesuppressant on another. The occurrence of interstitial lung involvement requires the immediate introduction of
immunosuppressants in addiction to CS. Severe
dysphagia seems to improve with
intravenous immunoglobulins (Ig).
Physical therapy could be started after the acute phase of diseases and seems to have a beneficial role in muscle strength recovery.