Diagnosis

In most of these cases, fatigue can be relieved with adequate rest. It is important to note that longstanding fatigue can be the harbinger of a serious medical or psychological problem. A number of more serious conditions may cause persistent fatigue and other symptoms of CFS and should be ruled out. Patients and doctors should not overlook these diseases, even if they have been previously treated, because they may not have completely resolved or may cause residual fatigue. Doctors can usually distinguish these diseases from CFS after a clinical evaluation and laboratory testing.

Infectious Mononucleosis and Epstein-Barr Virus. Infectious mononucleosis is marked by fatigue and swollen glands. It primarily affects adolescents and young adults. Some patients may have lingering fatigue that lasts for many months and blood tests that indicate a persistence of the Epstein-Barr virus (EBV), which causes mononucleosis.

In some people with CFS, there may be no direct link to Epstein-Barr virus. Many healthy persons without CFS have the same signs of low-level EBV infection, and, conversely, many patients with CFS show no signs of EBV infection. In others, however, the virus may play a role. Research published in 2005 shed new light on ways in which latent Epstein-Barr virus may cause immune problems and CFS-like symptoms.

Autoimmune Diseases. Some diseases, including systemic lupus erythematosus, multiple sclerosis, and rheumatoid arthritis, are caused by autoimmunity, a condition in which the person's immune system attacks the body's own tissues. The early symptoms of these conditions may mimic some of those that appear in CFS, such as muscle and joint pain and fatigue. These diseases, like CFS, also occur more often in women than in men. Autoimmune diseases evolve slowly, and even if a diagnosis of chronic fatigue syndrome is considered, doctors should keep track of any changes in symptoms over time in order to rule out these serious illnesses. It should also be noted that some experts are concerned that many patients who actually have CFS will be mistakenly diagnosed with these diseases, particularly multiple sclerosis, and subjected to unnecessary treatments.