Screening for RNF5 expression in muscle biopsies from patients suffering from muscular disorders including classical myopathies such as Duchenne and Becker myopathy as well as other myopathies with unknown etiology identified upregulation and mislocalization of RNF5 to aggregates in muscles from sIBM patients, as well as in a mouse model for hereditary IBM. This evidence concerns the gene RNF5 and inclusion body myositis.