Autoantibodies targeting the Mi-2 nuclear antigen represent one of the serologic hallmarks of idiopathic inflammatory myopathies, with a diagnostic sensitivity and specificity of approximately 4-18% and 98-100%, respectively. Mi-2 antigen is a component of the nuclesome remodeling-deacetylase (NuRD) complex involved in transcription regulation.Anti-Mi-2 antibodies are strongly associated with dermatomyositis (frequency up to 31%) and have a very high positive predictive value for such disease subset. A strong correlation with HLA-DR7 has been demonstrated. At the moment, optimal serologic testing is achieved by ELISA screening on recombinant Mi-2 antigen and confirmation of positive results on immunoblot.