PATHOGENIC TRACKS IN FATIGUE SYNDROMES

This review analyses the recent literature devoted to two related fati gue syndromes: chronic fatigue syndrome (CFS) and acute onset postvira l fatigue syndrome (PVFS). The articles are grouped into five pathogen ic tracks: infectious agents, immune system, skeletic muscle, hypothal amo-pituitary-adrenal (HPA) axis and psychiatric factors. Although a p articular infectious agent is unlikely to be responsible for all CFS c ases, evidence is shown that host-parasite relationships are modified in a large proportion of patients with chronic fatigue. Antibody titre s against infectious agents are often elevated and replication of seve ral viruses could be increased. Chronic activation of the immune syste m is also observed and could be due to the reactivation of persistent or latent infectious agents such as herpes viruses (i.e. HHV-6) or ent eroviruses. It could also be favorised by an impaired negative feedbac k of the HPA axis on the immune system. A model is proposed where the abnormalities of the HPA axis are primary events and are mainly respon sible for a chronic activation of the immune system which in turn indu ces an increased replication of several viruses under the control of c ellular transcription factors. These replicating viruses together with cytokines such as TNF-alpha would secondarily induce functional disor ders of muscle and several aspects of asthenia itself.