CFS and EBV

Chronic fatigue syndrome (CFS) is a disorder characterized by a state of chronic fatigue that persists for more than 6 months, has no clear cause, and is accompanied by cognitive difficulties. It was initially termed encephalomyalgia (or myalgic encephalomyelitis) because British clinicians noted that the essential clinical features of CFS included both an encephalitic component (manifesting as cognitive difficulties) and a skeletal muscle component (manifesting as chronic fatigue).
Various unrelated infectious diseases (eg, pneumonia, Epstein-Barr virus [EBV] infection, diarrhea, upper respiratory tract infections) appear to lead to a state of prolonged fatigue in some persons. Generally, if this condition is accompanied by cognitive difficulties, it is referred to as CFS.
The cause of CFS is unknown, but the disorder is probably an infectious disease with immunologic manifestations. EBV has been excluded as a cause of CFS, even though EBV infection is one of the many causes that may lead to a state of chronic fatigue. CFS is not synonymous with chronic EBV infection or chronic infectious mononucleosis.
Because no direct tests aid in the diagnosis of CFS, the diagnosis is one of exclusion but that meets certain clinical criteria, which are further supported by certain nonspecific tests. The diagnosis of CFS also rests on historical criteria (ie, otherwise unexplained fatigue for more than 6 months accompanied by cognitive dysfunction). The absence of cognitive dysfunction should exclude CFS as a potential diagnosis.
Because no cause of CFS has been determined, no effective therapy exists for CFS.
For patient education resources, see the Back, Ribs, Neck, and Head Center, as well as Chronic Fatigue Syndrome, Fibromyalgia, and Fatigue.

Diagnostic criteria

According to the Centers for Disease Control and Prevention (CDC),^[1] in order to receive a diagnosis of CFS, a patient must (1) have severe chronic fatigue of at least 6 months’ duration, with other known medical conditions excluded by clinical diagnosis, and (2) concurrently have 4 or more of the following symptoms:

• Substantial impairment in short-term memory or concentration
• Sore throat
• Tender lymph nodes
• Muscle pain
• Multijoint pain without swelling or redness
• Headaches of a new type, pattern or severity
• Unrefreshing sleep
• Postexertional malaise lasting more than 24 hours

The symptoms must have persisted or recurred during 6 or more consecutive months of illness and must not have predated the fatigue.
The CDC case definition also states that any unexplained abnormality detected on examination or other testing that strongly suggests an exclusionary condition must be resolved before further classification is attempted. Conditions that do not exclude CFS include the following:

• Any condition defined primarily by symptoms that cannot be confirmed by diagnostic laboratory tests, including fibromyalgia, anxiety disorders, somatoform disorders, nonpsychotic or melancholic depression, neurasthenia, and multiple chemical sensitivity disorder
• Any condition under specific treatment sufficient to alleviate all symptoms related to that condition and for which the adequacy of treatment has been documented, including hypothyroidism for which the adequacy of replacement hormone has been verified by normal thyroid-stimulating hormone levels, or asthma in which the adequacy of treatment has been determined by pulmonary function and other testing
• Any condition, such as Lyme disease or syphilis, that was treated with definitive therapy before development of chronic symptoms
• Any isolated and unexplained physical examination finding, or laboratory or imaging test abnormality that is insufficient to strongly suggest the existence of an exclusionary condition, including an elevated antinuclear antibody titer that is inadequate, without additional laboratory or clinical evidence, to strongly support a diagnosis of a discrete connective tissue disorder

In children, CFS is poorly defined. Most studies of CFS in the pediatric age range have followed the CDC criteria. However, whether the adult CDC case definition can be applied to children and adolescents is debatable.
Children have typically been referred to specialty clinics after extensive screening by their primary care physician has yielded negative or nonspecific test results. Therefore, common short-lived causes of fatigue are effectively excluded. The length of fatigue (6 months) also effectively excludes many common illnesses and probably should be retained in any forthcoming pediatric case definition.