POLYMYOSITIS AND DERMATOMYOSITIS - NO PERSISTENCE OF ENTEROVIRUS OR ENCEPHALOMYOCARDITIS VIRUS-RNA IN MUSCLE

Objectives-A persistent infection of enteroviruses and cardioviruses h as been implicated in polymyositis and dermatomyositis, but convention al hybridisation studies of the presence of enterovirus RNA and encaph alomyocarditis (EMC) virus RNA in affected muscle have yielded conflic ting results. To investigate further the possibility of viral persiste nce, the presence of viral RNA in muscle from patients with adult onse t polymyositis and dermatomyositis was investigated using a polymerase chain reaction (PCR) technique. Methods-Muscle tissue was obtained fr om 10 patients with polymyositis and five patients with dermatomyositi s, all with adult onset active disease. A PCR was performed using prim ers with high specificity for enterovirus and EMC virus RNA, followed by Southern blot hybridisation with an oligonucleotide probe directed against the internal portion of the amplified product. A PCR directed against the Abelson tyrosine kinase mRNA served as an internal control for the presence and quality of RNA. Results-A specific amplification for enterovirus or for EMC virus could not be seen in any of the musc le biopsy samples, despite a sensitivity of about 30 plaque forming un its for enterovirus and of 100 plaque forming units for EMC virus. Sou thern blot hybridisation confirmed these results in that positive cont rols hybridised with the oligonucleotide probe, but no signal was obta ined with the muscle specimens. Conclusion-A sensitive and specific PC R technique showed no evidence of the presence of enterovirus or EMC v irus RNA in muscle samples from patients with polymyositis or dermatom yositis. These data do not support the proposal that viral RNA persist ence plays a part in these idiopathic inflammatory myopathies.