Screening for antibodies against the Mi-2β antigen is performed in patients with the potential for polymyositis, dermatomyositis and overlap syndrome.
Antibodies against the Mi-2 protein are associated with classical dermatomyositis and are detected in 30% of patients. Antibodies against Mi-2 can also be detected in a small proportion of patients with polymyositis (<10%). The Mi-2 antigen contains two chains, and patients may have antibodies against the Mi-2α or even against the Mi-2β antigen chains. There is no known clinical difference between the antibodies directed against the two different Mi-2 chains.