Screening for antibodies against the MDA5 antigen is performed to investigate polymyositis, dermatomyositis, and overlap syndrome.
Antibodies against the MDA5 antigen occur in approximately 70% of patients with dermatomyositis, where muscle weakness may be mild with normal levels of CPK (creatine kinase) (amyopathic dermatomyositis). MDA5 antibodies (or CADM140 antibodies because they are directed against an antigen with a molecular weight of 140 kDa) are closely associated with rapidly progressive interstitial lung disease.
