This video describes the signs, symptoms, diagnosis, aetiology, syndromic condition, myositis. Myositis means inflammation of the muscles that you use to move your body. An injury, infection, or autoimmune disease can cause it. Two specific kinds are polymyositis and dermatomyositis. TIMELINE: 0:12 Introduction 0:36 Definition 1:54 Most affected muscle 3:06 Signs and symptoms 4:22 Diagnosis 5:23 Etiology 7:18 Syndromic conditions 8:13 Drug-induced myopathy 8:54 Excessive physical effects 9:48 Myositis and arthritis 11:28 End