Clinical features of Japanese patients with inclusion body myositis.

[inclusion body myositis]

The incidence of sporadic inclusion body myositis (sIBM ) has been much lower in Japanese than in Western populations . Because of a few reports on Asian populations , it is unclear whether the clinical characteristics of sIBM are identical in Caucasian and Japanese patients .We compared 18 patients with sIBM , divided into 3 groups by age-of-onset , with previous cohort studies . We calculated the ΔIBM functional rating scale /time duration (ΔIBMFRS /Δtime ) as an index of functional disability progression . Patients ' electrophysiology was analyzed in relation to their clinical characteristics .The cohort was 83 .3 % male and showed uniform initial muscle weakness in the lower and /or upper limbs . An older age-at -onset was associated with a more rapid progression , and patients with a longer duration frequently showed F-wave abnormalities and findings of chronic denervation .The clinical characteristics of sIBM were relatively homogeneous beyond the ethnic differences . Aging might be a synergistic factor for the progression of sIBM pathology .