Update: Biomarkers for idiopathic inflammatory myopathies

Purpose of Review: Establishing diagnoses and distinguishing active disease from chronic injury remain significant clinical challenges in idiopathic inflammatory myopathies (IIM). Recent 'discovery' approaches utilizing novel genomic and proteomic techniques have revealed candidate molecular biomarkers to augment clinical and classical histological data. Recent Findings: Whole blood and serum Type 1 interferons (IFN-1) and IFN-1 inducible genes are gaining traction as disease biomarkers in IIM. IFNβ is emerging as a disease activity marker specifically for dermatomyositis. Recently, molecules associated with innate immune-cell function, including TLR-3, high mobility group box (HMGB)-1, B7 Homolog 1, S100A4, and resistin have been detected in tissues of dermatomyositis patients. Serum Interleukin-17 (IL-17) and IL-23 correlate with active disease in early IIM. Antibodies recognizing the Survival Motor Neuron complex have been newly identified in a subset of patients with polymyositis. Protein aggregates are potential disease activity sensors for inclusion body myositis. Skin and lung harbor potential biomarkers for IIM. Summary: Recent advances in understanding the pathogenesis of IIM have led to discovery of molecules that are candidate biomarkers of disease activity. Type 1 interferon and myeloid-cell signatures are leading candidate markers for use in IIM activity monitoring.