Screening for antibodies against the Mi-2 alpha antigen is performed when investigating patients with possible 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-2 alpha or even to the Mi-2 beta antigen chains. There is no known clinical difference between the antibodies directed against the two different Mi-2 chains.
See also: Mi-2 beta Antibodies