Objective. To investigate for the presence of increased titers of circulating antibody to putative infectious agents and for detectable viral RNA or bacterial DNA in children with active recent-onset juvenile dermatomyositis (DM).Methods. Magnetic resonance imaging-directed muscle biopsies were performed in 20 children with active, untreated, recent-onset juvenile DM and in age-matched children with neurologic disease. Sera were tested for complement-fixing antibody to Coxsackievirus B (CVB), influenza A and B, parainfluenza 1 and 3, Mycoplasma pneumoniae, mumps, respiratory syncytial virus, and Reovirus; and by immunofluorescence for IgG antibody to Toxoplasma gondii cytomegalovirus and IgM antibody to Epstein-Barr virus. Muscle from juvenile DM patients and control children, CD-1 Swiss mice with and without CVBl infection, and viral stock positive for CVB1-6 were tested using reverse-transcriptase polymerase chain reaction with 5 primer sets, 4 probes

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