Long term functional outcome of idiopathic inflammatory myopathies

The idiopathic inflammatory myopathies (IIM) comprise a group of diseases characterized by chronic inflammation of the skeletal muscles. The definition of the long-term outcome of IIM, has been limited by the difficulty in objectively evaluating the rate of muscle function impairment. Aim of our study, was to define the long term outcome in a group of 37 IIM patients, followed at our centres between 1979 and 1999. A protocol, evaluating CK levels, muscle function, and disability in daily life activity was prospectively designed. The disease outcome was defined on the basis the patient’s functional evaluation. Disease activity was defined as the presence of an increase in serum CK levels associated with an increase of therapy. At the end of follow up, 27% of the patients had an active disease and 35% had a poor functional outcome. On the basis of our results we could distinguish three different outcomes of IIM: (i) good functional outcome (65%); (ii) poor functional outcome with inactive disease (13.5%); (iii) poor functional outcome and active disease (21,5%). In conclusion, although IIM seem to have a good evolution in terms of disease activity, in about 46% of patients they are associated with an elevated incidence of functional impairement, probably attributable both to the disease’s damage and to the side effects of therapy.