Many doctors and researchers are convinced that Fibromyalgia Syndrome (FMS) and Chronic Fatigue Syndrome (CFS) are simply different manifestations of the same underlying disorder. In fact, many patients suffer from both conditions. While both have been acknowledged as real physical diseases, neither one has a known cause or cure. Is the lack of a cure all that the two illnesses have in common? Not by a long shot. When looking at what is known about FMS and CFS, they appear to be more alike than they are different.

Fibromyalgia means pain in the fibrous tissues of the body--the muscles, ligaments and tendons. FMS used to be called fibrositis, which implied that there was inflammation in the muscles, but recent research has proved that there is no inflammation. FMS does not damage the tissues and is not progressive. Because various other symptoms often accompany the muscle pain, it's often called Fibromyalgia Syndrome. Routine laboratory tests usually reveal nothing abnormal in patients with FMS. However, FMS sufferers are sensitive to pressure in specific areas of the body called "tender points."
In 1990 the American College of Rheumatology established formal criteria for diagnosing Fibromyalgia (primarily for research purposes). To meet the diagnostic criteria, patients must have:
1. Widespread pain in all four quadrants of the body for at least three months
2. At least 11 of the 18 specified tender points
Other common symptoms associated with Fibromyalgia include fatigue, sleep disorder, cognitive impairments, numbness and tingling sensations, irritable bowel symptoms, and more.

For both FMS and CFS, patients should be evaluated for other problems that could be causing the symptoms, such as low thyroid function, iron deficiency, arthritis, and other medical conditions.
A CFS diagnosis as opposed to one of FMS often depends merely on whether fatigue or pain is the most dominant symptom. Although there are certain symptoms--such as fever, sore throat, and swollen glands--that are found more commonly in CFS than in patients with FMS, the similarity in symptoms between the two conditions is undeniable. In addition, research has revealed similar physical abnormalities in CFS and FMS, such as reduced blood flow in key areas of the brain. Technologies for analyzing brain function such as SPECT and PET scans have documented these abnormalities, and there is little difference between the scans of CFS sufferers and those of FMS patients. What is still unclear is whether these abnormalities are a result or the origin of the disease.

Similarities Between CFS and FMS

Other similarities between the two syndromes can be summarized as follows:

Both disorders affect people of any age and gender, but they are more common among women.
The two conditions can be extremely debilitating, though their symptoms are largely invisible.
Onset often occurs during childbearing years.
Many symptoms are common to both illness groups, including headaches, numbness or tingling, dizziness, irritable bowel, cognitive problems, and more.
Most sufferers have sleep disorders, such as "alpha-delta" or unrefreshing sleep.
Symptoms wax and wane, and flare-ups can be triggered by stress.
Viruses or traumatic injury have been suspected as triggers.
Immune system and/or neuroendocrine system abnormalities are thought to be a possible underlying cause of the disorders.
Differences Between CFS and FMS
Some of the key differences between Chronic Fatigue Syndrome and Fibromyalgia are as follows:

FMS is more prevalent, affecting at least 2 percent of the population in the United States. CFS prevalence numbers vary; the CDC claims that CFS affects at least .2 percent of the population, while recent research reveals estimates that are twice that number.
Specific tender points are the hallmarks of FMS and are used for diagnosis, while CFS is a "diagnosis of exclusion" in which any other potential causes of the symptoms must be ruled out.
There is some evidence that graded aerobic exercise improves muscle function and reduces pain in FMS but exercise is often impossible for, and may even hinder, CFS patients.
Source: OnHealth
Overlapping Syndromes

A number of researchers have studied the relationship between CFS and FMS. Dr. Muhammad Yunus from the University of Illinois College of Medicine, views FMS and CFS as being part of a larger spectrum of conditions that he calls Dysregulation Spectrum Syndrome (DSS). Other researchers like Dr. Dedra Buchwald and Dr. Anthony Komaroff have shown that CFS and FMS overlap in patients by as much as 75%.

Furthermore, research has revealed that many associated disorders and underlying abnormalities are common to both illnesses. For example, in a 1998 review Dr. Robert Bennett points out that neurally mediated hypotension has been documented in both CFS and FMS. Similarly, abnormalities of the growth factor-1 axis have also been documented in both patient groups. A small 2000 study found a significant clinical overlap between the two illnesses: among females, 58% of fibromyalgia patients met the full CDC criteria for CFS, while for males this number was 80%. Finally, a study published in the Archives of Internal Medicine in January 2000 provided evidence that patients with CFS, FMS, and TMJ share key symptoms.

Current treatments for CFS and FMS are also similar and typically focus on enhancing the quality of sleep and controlling pain. Low doses of tricyclic antidepressants such as Elavil or Sinequan are often of some benefit.

Since the cause and ultimately the cure for CFS and FMS remain elusive, more information will be needed about both conditions before we can say with certainty that they are manifestations of a similar disease mechanism. In the meantime, researchers and practitioners can benefit from clinical investigation in both areas. Most of all, as patients who have one or both of these syndromes, we have a great deal to learn from each other.