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A persistent enterovirus infection in muscles may be to blame for some cases of chronic fatigue syndrome (sometimes called fibromyalgia) and others with chronic inflammatory muscle disease, a French team reports.

They detected genetic material (specifically RNA) from enteroviruses in 20 percent of muscle biopsies from patients with chronic inflammatory muscle diseases and 13 percent of patients with fibromyalgia/chronic fatigue syndrome, but not from healthy volunteers.

The findings favor a persistent infection involving defective viral replication as a cause of these conditions.

"The persistence of defective or infectious enteroviruses is well established for a lot of organs," Dr. Bruno Pozzetto from the University Hospital Center of Saint-Etienne, France, told Reuters Health.

Such infections have been documented in the heart, with possible involvement in heart enlargement; in pancreatic cells, possibly linked to juvenile diabetes; and in the central nervous system in association with a syndrome that afflicts aging survivors of polio, the researcher explained. "However, the link between these diseases, as well as chronic inflammatory muscle diseases, and viral persistence is not clear."

Pozzetto and colleagues investigated the presence of enterovirus in skeletal muscle biopsies from 15 patients with chronic inflammatory muscle diseases, 30 patients with fibromyalgia/chronic fatigue syndrome, and 29 healthy subjects to test their hypothesis that skeletal muscle may play host to persistent enteroviral infection.

Three patients with chronic inflammatory muscle disease and four patients with fibromyalgia/chronic fatigue syndrome were positive for enterovirus RNA, the team reports in the Journal of Medical Virology.

None of the muscle biopsies in this study contained a particular viral protein, the researchers note, which "suggests a defective viral replication."

It is too early to derive implications for treatment from these results, Pozzetto said.

However, he noted that so-called Coxsackie B viruses seem to play a key role in persistent muscular infections. "To prevent this persistence, an inactivated vaccine directed toward these viruses could be indicated."

Also, an antiviral agent called pleconaril, "acting during the early phases of the viral cycle, could also be useful in muscular diseases clearly associated with enterovirus." This is being tried in some cases of heart-muscle enlargement, Pozzetto said, but "it is too early to answer for muscular diseases."

SOURCE: Journal of Medical Virology, December 2003.

(Distributed by Yahoo! from Reuters news service).