Detection of HTLV-I provirus by in situ polymerase chain reaction in mononuclear inflammatory cells in skeletal muscle of viral carriers with polymyositis.

We tested for HTLV-I proviral DNA in skeletal muscle from patients with polymyositis infected with HTLV-I using the in situ polymerase chain reaction. We found the HTLV-I provirus in some of the CD4-positive cells in HTLV-I-positive polymyositis cases but not in HTLV-I-negative polymyositis ones. We could not detect HTLV-I within the muscle fibers. We suggest that HTLV-I-associated polymyositis is not due to direct, persistent infection of the muscle fiber by the virus, but to a T-cell-mediated immunological process triggered by the HTLV-I-infected cells.