Skeletal muscle involvement in tropical spastic paraparesis/HTLV‐1–associated myelopathy

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Abstract
The frequency of muscle involvement in TSP/HAM is not known, nor is the precise role that HTLV‐1 and the diverse cytokines play in the genesis of HTLV‐1–associated diseases. In order to better define the frequency and characteristics of the skeletal muscle involvement in TSP/ HAM, we studied 11 affected patients. EMG was performed in 9 patients and muscle biopsy was performed in all 11. Muscle tissue was analyzed using: reverse transcriptase PCR for interleukin‐1 in 8; PCR for HTLV‐1 proviral DNA in 5; and electron microscopy for viral particles in 3. We found pathologic alterations in all 11 patients. Four patients (36%) had a neurogenic process, while a primary muscle involvement was observed in the rest (64%). Four patients (36%) had polymyositis, and 3 (27%) had a noninflammatory myopathy. Muscle weakness in the upper limbs was significantly associated with inflammation in the muscle biopsy. EMG was abnormal in only 2 of 9 patients. Reverse transcriptase PCR did not demonstrate message for interleukin‐1 in any sample examined. PCR did identify HTLV‐1 proviral DNA in the muscle of 3 patients. Retroviral‐like particles were found, by EM, in only one biopsy. HTLV‐1 may play an important role in the pathogenesis of the frequent myopathies associated with HAM/TSP. © 1994 John Wiley & Sons, Inc.