Neurologists are from Mars. Rheumatologists are from Venus: Differences in approach to classifying the idiopathic inflammatory myopathies

Purpose of Review: Inflammatory myopathy (IIM) classification criteria have been the source of considerable debate. In the three decades since Bohan and Peter published their criteria which have long stood as the gold standard for diagnosis in clinical practice as well as inclusion into clinical trials, more sophisticated understanding of immunopathogenesis, histology, and specific autoantibody associations has broadened our understanding of these diseases. This editorial review examines the diverse approaches between different subspecialists in deriving appropriate IIM classification utilizing this updated knowledge. Recent Findings: Several investigators have proposed improved IIM classification criteria. More recently, larger scale consensus efforts have been undertaken by various expert groups including the European Neuromuscular Centre (ENMC) and The International Myositis Assessment and Clinical Studies Group (IMACS). The intent is to refine the classification criteria utilizing our enhanced understanding which has matured since the original publication of Bohan and Peter's proposal in 1975. Summary: Many diagnostic/classification criteria have been proposed for different forms of IIM over the last three decades. The majority of these have been based on clinical impressions rather than rigorous data analyses or expert consensus and none has been fully tested for sensitivity or specificity using appropriately powered studies that take into account relevant disease confounders. Different sets of criteria proposed and adopted by different specialties hamper the ability to compare clinical studies and assess clinical trials' outcomes. Large, multicentered, multispecialty studies are required to develop improved IIM criteria.