Misdiagnosis of Fibromyalgia: A Review of Cases Re-Diagnosed with Other Diseases

Fibromyalgia is a chronic pain syndrome associated with tenderness, mood disorders, poor sleep, and cognitive dysfunction. However, there is no established pathological basis for fibromyalgia, and its diagnosis is often difficult. To clarify the features and difficulties of diagnosing fibromyalgia, we conducted a review and meta-analysis of the outcomes of cases initially diagnosed with fibromyalgia. We accumulated previously published cases and data of newly recruited patients either for or against the outcomes by prospective or retrospective approaches. The presence of alternative diseases with the disappearance of fibromyalgia-like symptoms is well documented for cases of diverse ages and suggests that revised diagnoses may depend on patients' recall bias, selection bias, or the ideas of the physicians. Although discrepancies in the results were seen according to the type of case series, we preliminarily identified the most frequent diseases, such as hypothyroidism-like syndrome in adult patients and familial Mediterranean fever in child cases. The prevalence of fibromyalgia in patients with legitimate diseases should be reconsidered. Synopsis Fibromyalgia is a chronic pain syndrome associated with mood disorders, poor sleep, and cognitive dysfunction, and there is no established pathological basis and no currently available cure. The presence of diverse comorbid conditions and diverse symptomatologies within and between the comorbid conditions suggests that fibromyalgia may encompass more than one illness under one name. Our meta-analysis carefully demonstrates features of the diagnosis of fibromyalgia as follows: (i) the number of patients allocated to other diagnoses as a result of the revised diagnosis varied depending on the type of series of fibromyalgia cases; (ii) cases with congenital or chronic conditions, such as juvenile fibromyalgia, have legitimate diseases, and the rareness of the report suggests the referral and continuation bias of previous pediatric-based fibromyalgia research; and (iii) a chart-based study also demonstrated the entity bias for the diagnosis of fibromyalgia, similar to previous treatment-based and database studies, thereby suggesting that fibromyalgia may not be distinct from other disorders. Our meta-analytic result is well in concordance with some non-rheumatological studies analyzing cases diagnosed in a specialized pain therapy clinic, whose conclusions are generally contradictory to the criteria. The combination of the literature and the current study should further help emphasize the early and differential diagnoses of patients presenting with symptoms meeting the fibromyalgia criteria in the clinic. Future treatment-based and nosological studies may benefit from our suggestions to prevent undiagnosed comorbid diseases or syndromes.