FMS and CFS differences

At the time I wrote my article on the overlap between fibromyalgia and chronic fatigue syndrome, I was not aware of any research that showed up any physical differences. Since then a lot of new research has been published and some of it does seem to show how we can distinguish between CFS and FMS. I haven't done a comprehensive literature survey, but due to my interest in the topic I have begun collecting quotes and citations that I come across in my reading. Here are the first items in my collection:

Contents

Could the R-NaseL test pick the difference?
Disorders of pain perception

Note also that the Canadian "Fibromyalgia Guidelines", published as:

"Fibromyalgia Syndrome: Canadian Clinical Working Case Definition, Diagnostic and Treatment Protocols. A Consensus Document" in the Journal of Musculoskeletal Pain 11(4), 2004

may contain information to make a distinction. I haven't had the opportunity to read it yet (May 2004)

Postscript (2002):

Could the RNaseL test pick the difference?

Researchers led by Robert Suhadolnik in the USA and Kenny de Merlier in Belgium have made what looks like a real breakthrough in understanding CFS, resulting in a diagnostic test that may incidentally be able to distinguish between fibromyalgia and CFS patients.

RnaseL is an "antiviral pathway enzyme" that is produced by the body to attack viruses.  The blood test is based on the discovery by Dr. Robert Suhadolnik and his research team at Temple University of Medicine that up to 88% of CFS sufferers have abnormal "low molecular weight" RnaseL. R.J. Suhadolnik, D.L. Peterson, K. O'Brien et al., Biochemical evidence for a novel low molecular weight 2-5A-dependent RNase L in chronic fatigue syndrome. J Interferon Cytokine Res 17 (1997), pp. 377-385.

It is proposed that low molecular weight RnaseL is a marker for CFS.  Prof Kenny de Meirlier and R.E.D. Laboratories in Brussels (R.E.D stands for RNaseL Enzyme Dysfunction) have developed a blood test for low molecular weight RnaseL as a way of diagnosing CFS . The test is called the Fragmented Actin Serum Test (FASTest™). See  Detection of Actin Fragments in Serum: A Rapid Screening Test to Aid in the Diagnosis of Chronic Fatigue Syndrome on the RED Laboratories website.

The Belgian researchers confirmed Suhadolnik's finding that the majority of people who fit the standard CDC criteria for CFS have the low molecular weight enzyme. Interestingly, only a tiny fraction of the two control groups in their study - fibromyalgia patients and people with depression - had the enzyme. K. De Meirleir, C. Bisbal, I. Campine et al., A 37 kDa 2-5A binding protein as a potential biochemical marker for chronic fatigue syndrome. Am J Med 108 (2000), pp. 99-105. The implication could be that, unlike CFS, fibromyalgia is not associated with viral illness.

[ Contents ]

Disorders of pain perception

In "Pain in CFS" - Chapter 6 of A Consensus Manual for the Primary Care and Management of Chronic Fatigue Syndrome, Alan Lichtbroun, MD discusses pain in both CFS and FMS and picks out where the mechanisms are different:

"... we should realize that although significant differences exist between the two syndromes, many patients with CFS may have FMS. The concept of allodynia [oversensitive] pain processing is pivotal in understanding and treating the associated pain of both disorders". He says that a subgroup of CFS patients goes on to develop FMS.

Some of the main differences Lichtbroun describes are:

• People with FMS have four times as much nerve growth factor in their spinal fluid. This has to do with pain perception and it seems to be a special feature of FMS. Giovengo SL, Russell IJ, Larson AA. Increased concentrations of nerve growth factor in cerebrospinal fluid of patients with fibromyalgia. J Rheumatol 1999;26:1564-9.
  
• People with FMS have low levels of serotonin and its metabolites in their cerebral spinal fluid, blood and urine, but people with CFS have high plasma levels of serotonin metabolites. Serotonin is an anti-nociception neurochemical, so if you lack it you feel more pain. And people with FMS do have lower pain thresholds than people with CFS.
  Vaeroy H, Helle R, Forre O, Kass E, Terenius L. Elevated CSF levels of substance P and high incidence of Raynaud phenomenon in patients with fibromyalgia: new features for diagnosis. Pain 1988;32:21-6. Kang Y-K, Russell UJ, Virpaio GA, et al. Low urinary 5- hydroxyindoleacetic acid in fibromyalgia syndrome: evidence in support of a serotonin-deficiency pathogenesis. Myalgia 1998;1:14-21.
  Russell IJ, Orr MD, Littman B, et al. Elevated cerebrospinal levels of substance P in patients with fibromyalgia syndrome. Arthritis and Rheumatism 1994;37:1593-601.
• People with CFS have different results to tilt table tests than people with FMS (this measures whether your blood pressure falls when you stand up and shows whether your brain is controlling your blood pressure properly).
  Itzhak R, Rosenbaum M, Jochana N, et al. Cardiovascular response to upright tilt differs in FMS from CFS. Arthritis and Rheumatism 2000;23:S209.
• People with CFS have different results to SPECT or PET scans of the blood flow in their brains.

Lichtbroun sums up:

" ... findings suggest that both FMS and CFS are characterized by alterations in neural processing of sensory information. On the other hand, neuroendocrine studies suggest that in FMS hyperexcitability of the spinal NMDA receptors increases ascending sensory transmission to the brain that enhances pain perception. Persons with CFS usually experience musculoskeletal pain, but they do not show abnormal sensitivity to pressure stimulation at multiple anatomic sites, unless they also meet the criteria for FMS."

Roughly translated, "The way the brain processes what you feel, see etc is going wrong in both CFS and FMS. However research into brain chemicals like serotonin seem to show that people with FMS are also more sensitive to pain in particular. That's why they have the fibromyalgia "tender points" while people with CFS don't."

Lichtbroun also says:

"... immune modulation appears to be important in both disorders. CFS appears to be promoted by a TH 2 response. Activated T helper cells from patients with CFS, unlike those of FMS, produce fewer TH 1 cytokines and produce more IL-5 and TH 2 type cytokines (to preferentially stimulate cells to produce antibodies). When FMS pain arises, substance P appears to stimulate other cytokines, such as IL-8 and IL-6. Since IL-8 produces myopathic pain, IL-6 induces hyperalgesia. It is hypothesized that they play a role in modulating FMS pain syndrome in CFS patients."

(I'm not going to attempt to translate that!)

These are all very interesting. It's worth noting two things: firstly, it's only possible to compare the mechanisms where research on the same thing has been done on both FMS and CFS patients. In other cases we may know something about how x operates in CFS, or levels of y in FMS ... and not know if this applies to the other syndrome or whether this is a point of difference. Secondly, there is still a lot of uncertainty. There are some people who are diagnosed as having both CFS and FMS, and this is bound to muddy the waters when it comes to identifying differences. What we may be doing is clarifying subsets of one overall syndrome.

Source: Alan Lichtbroun, MD "Pain in CFS" in A Consensus Manual for the Primary Care and Management of Chronic Fatigue Syndrome ed. Joseph F John, Jr.; Academy of Medicine of New Jersey and New Jersey Dept of Health and Senior Services; 2002 [PDF download 758kb]

[ Contents ]

Although I believe strongly in joint advocacy for overlapping syndromes, I'm excited by the differences that seem to be identified by the research. Whether the results are the same for all patients or point up differences between them, this research into the pathophysiology of CFS and FMS has the potential to lead to effective treatment of individuals whatever their diagnosis.

[ Contents ]

HOME  > Library

        Webmaster      last revised 12 May, 2004