Dermatomyositis

Dermatomyositis (DM) is a systemic autoimmune condition characterized by muscle and skin inflammation. Proximal muscle weakness and characteristic skin rashes dominate the clinical picture. However, pulmonary, renal, and esophageal involvements can also be observed. An increase in serum levels of muscle enzymes and characteristic electromyographic and imaging findings are important in the diagnostic workup and in the follow-up of DM patients, while muscle biopsy remains important especially in patients without specific skin rashes. Myositis-specific antibodies (MSA) are disease-specific markers, which are becoming increasingly central in the diagnosis and management of DM. MSA allow for early recognition of DM even before the onset of clinically overt myositis, allow the identification of homogeneous subgroups of DM patients, and predict treatment response. Notwithstanding their potential, MSA detection is still poorly standardized and expensive. Over the years, several diagnostic and classification criteria have been proposed to aid clinicians and researchers to correctly identify patients with this rare disease. The 2017 EULAR/ACR classification criteria represent the latest effort of the scientific community in this direction, proving to perform better than their predecessors.