Muscle Architecture in Chronic DM and PM

Dermatomyositis (DM) and polymyositis (PM) are diseases that cause muscle inflammation leading to muscle damage and weakness. While some patients return to normal after being treated with medications, the large majority of patients suffer from chronic muscle weakness and disability. A better understanding of why this happens despite treatment will allow more effective and targeted therapies to be developed in the future. Muscle inflammation and/or its treatment may lead to certain changes in muscle architecture that contribute to ongoing muscle weakness in DM/PM patients. We will enroll 20 participants with DM/ PM and 10 healthy participants will be enrolled in this study over an 18 month period. Study partiCipants will be interviewed and examined. They will also undergo a series of tests that will allow us to study their muscle strength and structure. The results of this study will allow us to determine the contributors to long-term muscle weakness and develop treatment approaches to prevent disability in DM/PM patients.