CFS versus FM: Twins, Cousins, or Just Acquaintances?

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By Charles W. Lapp, MD

Editor's Note: Dr. Lapp is Director Emeritus of the Hunter-Hopkins Center in Charlotte, one of the few medical practices in the US specializing in the treatment of ME/CFS and fibromyalgia.

Chronic Fatigue Syndrome is a disorder characterized by debilitating fatigue and recurrent flulike symptoms, such as muscle and joint aches, sore throat, swollen glands, and difficulty thinking. Fibromyalgia Syndrome is a disorder characterized by widespread muscle pain. Can such different descriptions share anything in common?
 

Siamese Twins

Most experts agree that the symptoms of CFS and FM are so close that they are - for all intents - the same disorder. It's a bit like Jekyll and Hyde, or perhaps like Chang and Eng Bunker, the Siamese twins made famous by P.T. Barnum. They were both the same "person" but had two different names, two similar but different personalities.
 

Assigning a Diagnosis

Patients who present to their primary care providers frequently relate a litany of complaints such as fatigue, vague aching, and trouble with memory or concentration.

Based on these complaints, the primary care doctor will most likely diagnose Chronic Fatigue Syndrome using the 1994 international case definition published by the Centers for Disease Control.

On the other hand, the patient whose major complaint is pain will likely consult a rheumatologist who will ask, "where does it hurt?" When it is determined that the patient hurts at the classical "tenderpoints" defined by the ACR [American College of Rheumatology] in 1990, the likely diagnosis will be Fibromyalgia.
 

Overlaps and Shadows

So one diagnosis is frequently given by primary care physicians and the other by rheumatologists. Both diagnoses have several features in common: exertional malaise [activity intensifying symptoms], cognitive difficulties, muscle pain (or myalgias) and a sleep disorder.

Both are frequently associated with "overlap disorders" or "shadow syndromes," as I like to call them. The most common "shadow syndromes" are irritable bowel syndrome, irritable bladder, temporomandibular dysfunction, and mitral valve prolapse.

Others include premenstrual syndrome, primary dysmenorrhea, migraine, restless legs or periodic leg movements, Myofascial Pain Syndrome (MPS), chemical sensitivities, autonomic dysfunction (Neurally Mediated Hypotension and Postural Orthostatic Tachycardia Syndrome), Gulf War Syndrome, and possibly hyperextensibility, acne rosacea, Raynaud's phenomenon, sicca complex (dry eyes and mouth) and vasomotor rhinitis (constant runny nose and congestion).

Note that the shadow syndromes occur predominantly in females, are defined clinically rather than by physical or laboratory findings, and many are associated with either pain or fatigue. It is likely that these disorders occur concurrently because they share a common biophysiological thread.
 

Fibromyalgia & CFS Compared

The symptoms are similar for both syndromes, including debilitating fatigue, post-exertional malaise, feverishness, sore throat, headache, joint aches, a feeling of generalized weakness, subjective swelling, non-radicular paresthesias (numbness or tingling that does not follow typical nerve patterns), memory loss, forgetfulness, confusion, irritability, and depressed mood.

There are some subtle differences, however. (See Table 1 at end of article.) Historically, CFS is frequently triggered by a flulike or infectious illness, but sometimes occurs after trauma or surgery. FM, on the other hand, is frequently triggered by trauma, less often by an infectious process.

While there is a preponderance of women in both disorders, women are more likely to have FM (9:1) than CFS (7:3). The median age for both disorders is about 40 years, although all age groups are vulnerable, including children and seniors. Familial aggregations and overlapping HLA haplotypes are described for both disorders.

Physiologically, both disorders have in common reduced midbrain and cortical blood flow; autonomic dysfunction such as symptomatic orthostatic tachycardia and neurally mediated hypotension; suppression of the hypothalamic pituitary axis; disturbed Stage 4 sleep; reduced serum or CSF serotonin levels; and suppression of growth hormone, somatomedin C, or IGF1. (Similarities are summarized in Table 2.)

Substance P, a neurotransmitter responsible for the transmission of pain is elevated in persons with FM (but not CFS); and RNaseL, a cellular antiviral enzyme is frequently elevated in CFS (but not in FM). These differences may reflect why pain is a key symptom in FM, and viral symptoms predominate in CFS.
 

Treatment

The treatment of CFS and FM is hampered by the absence of a known cause and pathophysiology. In such instances, treatment is generally limited to supportive care and symptomatic therapy. Thus a prudent diet, basic supplementation, and traditional management of sleep disruption, pain, and autonomic symptoms are the standard course.

Counseling is helpful in coping with chronic illness and stress, and study after study has extolled the virtues of low level progressive exercise. Activity must be approached cautiously, however.

"Pure cases" of FM seem to respond with increased endurance and improved well-being to a progressive exercise program, while "pure cases" of CFS are more likely to respond with increased cognitive and flulike symptoms to a similar regimen. Thus, persons with CFS may have to start at a lower level and progress more slowly.
 

Pure Cases

There are certainly cases of "pure CFS" or "pure FM." When there is no significant complaint of muscle pain, the patient would be diagnosed as having "pure CFS," mostly characterized by fatigue, cognitive dysfunction, sleep disruption, and flu-like symptoms including vague muscular aching during relapses.

When cognitive symptoms are minimal and widespread muscle pain is the major complaint, the patient is thought to have "pure FM." These make up a minority of the cases, however, since about 70% of persons with CFS meet criteria for FM, and about 70% of persons with FM also meet criteria for CFS.

In most aspects Fibromyalgia and CFS are almost identical. There are subtle differences in biochemistry, prevalence, and perhaps response to exercise that separate them ever so slightly. CFS and FM may represent the extreme ends of a spectrum of multisystem disorders characterized by fatigue, pain, and female predominance.
 

Table 1: Differences

Table 2: Similarities

• Reduced cerebral blood flow in cortex and midbrain
• HPG Axis suppression
• Non-restorative sleep
• Reduced serum and/or CSF serotonin
• Low growth hormone
• Familial aggregation / haplotypes