Not All That Hurts Is Fibromyalgia: The Challenges of Differential Diagnosis of Patients Referred to a Tertiary Care Center

Background/Objectives: Fibromyalgia (FM) is a complex and disabling condition characterized by chronic widespread pain, fatigue and multiple somatic symptoms, often overlapping with rheumatic (RMD) and non-rheumatic diseases. Since objective biomarkers are lacking, diagnosis relies on validated criteria and careful clinical assessment. This study aimed to describe a referral cohort including patients with either a previous diagnosis or suspicion of FM and to identify the proportion of patients fulfilling FM criteria, the severity of their FM, and to identify alternative or associated conditions. Methods: A prospective cohort of consecutive patients referred to our Center between June 2023 and October 2025 was assessed according to the 2016 American College of Rheumatology (ACR) diagnostic criteria for FM. Demographic data, medical history, and clinical findings were collected. Additional laboratory or imaging investigations were performed when clinically indicated. FM severity was evaluated using validated tools included in the 2016 ACR diagnostic criteria. Results: Overall, 247 patients were enrolled: 44 with a certified previous FM diagnosis, 145 referred by physicians for suspected FM and 58 self-referred. Among patients without a previous certified diagnosis, FM was newly diagnosed in 75% of physician-referred and 77% of self-referred patients. A substantial proportion was also diagnosed with an RMD. Longer symptom duration, higher fatigue and worse global health were associated with FM. Conclusions: Among patients who reached our referral center because of suspected FM, a high proportion fulfilled the 2016 ACR criteria. Careful application of FM criteria and evaluation of coexisting conditions may improve timely diagnosis and management.