Unrecognised Burden: High Prevalence and Clinical Impact of Fibromyalgia in Functional Motor Disorder

BackgroundFibromyalgia is a chronic pain disorder, affecting 2-3% of the population, characterised by widespread pain, fatigue, sleep and cognitive symptoms. Despite symptom overlap between functional motor disorder (FMD) and fibromyalgia, the prevalence of fibromyalgia in FMD and its impact on health-related quality of life (HRQoL) remain unclear. ObjectivesTo assess the prevalence of fibromyalgia in FMD using the 2016 American College of Rheumatology diagnostic criteria and to evaluate its impact on HRQoL. MethodsA total of 139 consecutive patients with clinically established FMD (115 females, mean age 44.6 (SD 11.3) years) completed Fibromyalgia Survey Questionnaire, subjective motor symptoms and HRQoL assessments. Motor symptoms were objectively rated using the Simplified FMD Rating Scale (S-FMDRS). Major physical illnesses, neurological, and psychiatric comorbidities, and the use of centrally acting and nociceptive pain medication was recorded. ResultsFibromyalgia was present in 44.6% of FMD patients (95%CI: 36.2-53.3%). Those with fibromyalgia had higher S-FMDRS scores (p < 0.01), lower HRQoL (p < 0.001), more frequent use of centrally acting and nociceptive pain medication (p < 0.01). Fibromyalgia severity was positively correlated with both subjective motor symptom severity (p < 0.01) and S-FMDRS (p < 0.05). Higher fibromyalgia severity (p < 0.001), S-FMDRS (p < 0.001), and psychiatric comorbidity (p < 0.001) were independent predictors of lower HRQoL. ConclusionsIn this study, fibromyalgia was common in FMD and associated with more severe motor symptoms, greater medication use and reduced quality of life, highlighting the importance of recognising and managing fibromyalgia in FMD.