HTLV-I proviral load correlates with progression of motor disability in HAM/TSP: Analysis of 239 HAM/TSP patients including 64 patients followed up for 10 years

To clarify clinical and laboratory findings that may be related to the path omechanism of HTLV-I-associated myelopathy/tropical spastic paraparesis (HA M/TSP), we analyzed these findings in 239 patients with HAM/TSP, including 64 patients followed up for 10 years after their first examinations, with s pecial interest in the HTLV-I proviral load in peripheral blood mononuclear cells (PBMCs), The proviral load in PBMCs did not differ in terms of modes of HTLV-I transmission, However, the proviral load in patients with age of disease onset greater than 65 years tended to be higher than those with a younger age of onset. In the 64 patients followed up for 10 years, the clin ical symptoms deteriorated in 36 patients (56%), unchanged in 26 patients ( 41%), and improved in 2 patients (3%). HTLV-I proviral load also appeared t o be related to the deterioration of motor disability in these patients, To our knowledge, the present study is the first longitudinal study concernin g the relationship between the clinical course of HAM/TSP and HTLV-I provir al load, It is suggested that HTLV-I proviral load is related to the progre ssion of motor disability and is an important factor to predict prognosis o f patients with HAM/TSP.