[Inclusion body myositis pathomechanism and therapy]

Inclusion body myositis is an acquired inflammatory muscle disease belonging to the family of idiopathic inflammatory myopathy with vacuole formation. Approximately 15-28% of idiopathic inflammatory myopathy patients suffer from inclusion body myositis. Early diagnosis is very important due to the slowly progressive disease course and consecutive muscle atrophy. Inclusion body myositis is the most common chronic progressive muscle disease over the age of 50 years. Both degenerative processes including beta-amyloid accumulation and inflammatory processes, such as CD8 positive T-lymphocytes mediated cellular cytotoxicity take part in the pathomechanism of the inclusion body myositis. These findings are well demonstrated by the parallel presence of vacuolized muscle fibers rarely invaded by T cells and intact muscle fibers invaded by inflammatory T-cells in biopsy specimens. MHC-I/CD8 complex was introduced into the newly revised diagnostic criteria as a specific immune marker which helps to differentiate inclusion body myositis from aspecific inflammation present in other muscle dystrophies. Clinically both proximal and distal muscle weakness, respiratory muscle weakness and dysphagia are present. Interstitial lung disease is infrequent. Inclusion body myositis responds poorly to antiinflammatory treatment due to the predominant degenerative processes and it often results in only biochemical response instead of clinical. Diagnosis and differential diagnosis of inclusion body myositis are a very special challenge for the physician due to the diagnostic procedures which need immunohistochemical background. New therapeutic targets, monoclonal antibodies against the costimulatory molecules, anticytokine therapy may provide further improvement in the quality of life of inclusion body myositis patients.