Update on rheumatologic mimics of fibromyalgia.

Fibromyalgia is a common disorder of diffuse musculoskeletal pain. Several rheumatic diseases can mimic fibromyalgia, and a clinician would not want to miss these diagnoses because of their potential long-term sequelae, such as progressive joint damage or life- or organ-threatening disease if they remain untreated. This paper discusses the typical clinical presentations of selected rheumatic diseases (systemic lupus erythematosus, rheumatoid arthritis, ankylosing spondylitis, polymyalgia rheumatica, and osteoarthritis) then highlights the key features in history, laboratory testing, and radiographic imaging that aid the clinician in differentiating between fibromyalgia and these rheumatic diseases.