Laboratory features—enzymes and biomarkers

This chapter describes the laboratory tests useful in diagnosing and monitoring patients with myositis. It describes creatinine kinase, it’s different isoforms and explains why this muscle enzyme is helpful in the diagnosis and monitoring of patients with inflammatory muscle disease. It also describes other skeletal muscle enzymes that are often elevated in both adult and juvenile onset disease and examines the specificity of troponins for cardiac muscle involvement. The prevalence and clinical utility of myositis specific and associated autoantibodies is explored, and we report the clinical features associated with different autoantibody subgroups, demonstrating how such autoantibodies can divide patients into clinically homogenous subgroups. Finally, evidence for the potential use of other novel biomarkers including cytokines is also explored.