[Recent progress in diagnosis and pathomechanism of inclusion body myositis]

Sporadic inclusion body myositis (sIBM) is an intractable and progressive skeletal muscle disease of unknown etiology and without effective treatment. Muscle biopsy typically reveals endomysial inflammation, invasion of mononuclear cells into non-necrotic fibers and rimmed vacuoles, suggesting inflammation and degeneration co-exist as part of the pathomechanism. We estimated the prevalence of sIBM in Japan is 1,000-1,500 in 2003 and an increase in the number of sIBM in Japan in the decade. TDP43 can be a whole mark of the muscle pathology of sIBM patients. Anti-cytosolic 5'-nucleotidase 1A (cN1A) can be a diagnostic marker of sIBM. Elucidation of the pathomechanism of sIBM is the most important to therapy. We'll also review the status of the therapeutics and clinical trials in sIBM.