Diagnostic confounders of chronic widespread pain: not always fibromyalgia

INTRODUCTION: Chronic widespread pain (CWP) is the defining feature of fibromyalgia (FM), a worldwide prevalent condition. Chronic widespread pain is, however, not pathognomonic of FM, and other conditions may present similarly with CWP, requiring consideration of a differential diagnosis. OBJECTIVES: To conduct a literature search to identify medical conditions that may mimic FM and have highlighted features that may differentiate these various conditions from FM. METHODS: A comprehensive literature search from 1990 through September 2016 was conducted to identify conditions characterized by CWP. RESULTS: Conditions that may mimic FM may be categorized as musculoskeletal, neurological, endocrine/metabolic, psychiatric/psychological, and medication related. Characteristics pertaining to the most commonly identified confounding diagnoses within each category are discussed; clues to enable clinical differentiation from FM are presented; and steps towards a diagnostic algorithm for mimicking conditions are presented. CONCLUSION: Although the most likely reason for a complaint of CWP is FM, this pain complaint can be a harbinger of illness other than FM, prompting consideration of a differential diagnosis. This review should sensitize physicians to a broad spectrum of conditions that can mimic FM.