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Arthritis and fibromyalgia are different diagnoses in that the latter lacks classic arthritic signs of joint damage. Problem is Fibromyalgia currently lacks definitive diagnostic tests and is instead diagnosed using a checklist of clinical symptoms that have changed dramatically since 1990 (see figure below from 1).

Thus unless diagnosed by an experienced rheumatologist, fibromylagia syndrome (FMS) could possibly be mis-diagnosed as seronegative arthritis. This is because in spite of such changes in clinical diagnostic criteria, varying proportion of rheumatoid arthritis patients are estimated to also have fibromyalgia:

  • 4 to 20% in the US (2, 3, 4, 5)
  • ~5% in Canada (6)
  • ~14% in Europe (7).

Obviously FMS diagnosis is applied to a heterogenous group of patients with heterogenous symptoms. At least one study could separate such patients into at least 4 clusters (8). Given that FMS diagnosis remains so iffy at best, the two things that matter most w.r.t. diagnosis and Rx are

  • One, whether there are some symptoms common across FMS? Answer seems to be yes, profound alterations in central pain mechanisms seem to be a common thread in all this diversity (9). As a result, the most consistent symptom attributed to FMS is chronic widespread pain. Other most common symptoms include morning stiffness, fatigue and non-restorative sleep (1, 10). Higher intensity pain with FMS is a key difference from arthritis (1, 11). Another striking difference is pain tends to be continuous in FMS compared to intermittent in arthritis (1).
  • Two, how such pain is managed. There the answer seems to be that regardless whether the diagnosis is FMS or just chronic widespread pain, treatment is identical the world over (12), namely, education, cognitive behavioral therapy, exercise and drugs, though not opiates (1). Drugs include Analgesic, Antidepressant, Anticonvulsant, Muscle relaxant, even Nonsteroidal anti-inflammatory drug. According to (1), the US Food and Drug Administration, but not the European European Medicines Agency, has approved Duloxetine, Milnacipran, Pregabalin for treating FMS. Since understanding of FMS is still preliminary enough to be considered a syndrome rather than a disease, most of these drugs reduce symptoms in only a small subset of patients while in others there’s either no change or change for the worse.

It’s rather sad that this is the state of affairs with FMS. The glass half-full aspect of it is that brain imaging studies showed considerable ‘objectively measurable abnormalities in brain structure and function, in particular pain processing, in patients with FMS’ (1). Thus, there’s no denying the condition is real, even if different patients report different symptoms and there’s as yet no definitive diagnostic test.


1. Borchers, Andrea T., and M. Eric Gershwin. “Fibromyalgia: a critical and comprehensive review.” Clinical reviews in allergy & immunology 49.2 (2015): 100-151

2. Yunus, Muhammad, et al. “Primary fibromyalgia (fibrositis): clinical study of 50 patients with matched normal controls.” Seminars in arthritis and rheumatism. Vol. 11. No. 1. WB Saunders, 1981.

3. Wolfe, F., and M. A. Cathey. “Prevalence of primary and secondary fibrositis.” The Journal of rheumatology 10.6 (1983): 965-968.

4. Wolfe, F., M. A. Cathey, and S. M. Kleinheksel. “Fibrositis (Fibromyalgia) in rheumatoid arthritis.” The Journal of rheumatology 11.6 (1984): 814-818.

5. Greenfield, Stuart, Mary‐Ann Fitzcharles, and John M. Esdaile. “Reactive fibromyalgia syndrome.” Arthritis & Rheumatism 35.6 (1992): 678-681.

6. Greenfield, Stuart, Mary‐Ann Fitzcharles, and John M. Esdaile. “Reactive fibromyalgia syndrome.” Arthritis & Rheumatism 35.6 (1992): 678-681.

7. Branco, Jaime C., et al. “Prevalence of fibromyalgia: a survey in five European countries.” Seminars in arthritis and rheumatism. Vol. 39. No. 6. WB Saunders, 2010. http://www.cnbc.pt/jpmatos/15.%2…

8. Vincent, Ann, et al. “OMERACT-based fibromyalgia symptom subgroups: an exploratory cluster analysis.” Arthritis research & therapy 16.5 (2014): 1. https://www.researchgate.net/pro…

9. Phillips, Kristine, and Daniel J. Clauw. “Central pain mechanisms in chronic pain states–maybe it is all in their head.” Best Practice & Research Clinical Rheumatology 25.2 (2011): 141-154. https://www.researchgate.net/pro…

10. McBeth, John, and Matthew R. Mulvey. “Fibromyalgia: mechanisms and potential impact of the ACR 2010 classification criteria.” Nature Reviews Rheumatology 8.2 (2012): 108-116.

11. Mengshoel, A. M., and Ø. Førre. “Pain and fatigue in patients with rheumatic disorders.” Clinical rheumatology 12.4 (1993): 515-521.

12. Toda, Katsuhiro. “Treatment of chronic widespread pain is similar to treatment of fibromyalgia syndrome throughout the world.” Journal of Musculoskeletal Pain 18.3 (2010): 317-318.