HTLV-1 in acquired adult myopathy

We report a 53-year-old Jamaican man with 20 years of progressing weakness involving proximal limb muscles and neck flexors. Serum CK was 1100 IU/L. EMG demonstrated spontaneous activity, myopathic motor units, and full recruitment patterns in weak muscles. Muscle biopsy revealed marked myofiber degeneration with extensive fibrosis, suggesting a chronic myopathic process. HTLV-1 antibody was present in serum in high titers by ELISA and Western blot. Immunohistochemistry with rabbit polyclonal antisera to HTLV-1 showed rare staining myocytes. PCR demonstrated HTLV-1 DNA in frozen muscle tissue. This myopathy, associated with HTLV-1 infection, has clinical and pathological features similar to a dystrophy. We recommend serological screening for HTLV-1 in cryptogenic adult myopathies.