Natural history of human T-lymphotropic virus 1-associated myelopathy -: A 14-year follow-up study

Background: The progression of neurological disability in human T-lymphotropic virus 1 (HTLV-1)associated myelopathy/tropical spastic paraparesis (HAM/TSP) remains undefined. Objectives: To determine the time course of disability scores and to identify predictors of outcome among patients with HAM/TSP. Design: Clinical 14-year follow-up study. Setting: University hospital. Patients: One hundred twenty-three patients with HAM/TSP. Main Outcome Measures: We determined time from onset to the following 4 Kurtzke Disability Status Scale (DSS) end points: scores of 6 (unilateral aid required), 6.5 (bilateral aid required), 8 (wheelchair confinement), and 10 (death related to the disease). Times to reach selected DSS scores were estimated using the Kaplan-Meier method. Univariate and multivariate analyses identified variables related to the rate of progression to DSS 8. The HTLV-1 proviral loads were also assessed. Results: The disability of the cohort progressed throughout the follow-up period. The median times from onset to DSS 6, 6.5, and 8 were 6, 13, and 21 years, respectively. The median time from DSS 6 to DSS 8 was 8 years; DSS 10 was reached by one fourth of the patients within 20 years. Age at onset of 50 years or older and high HTLV-1 proviral load were associated with a shorter time to DSS 8 (P = .01 and P = .02, respectively). A shorter time to DSS 6 significantly adversely affected the time to progression from DSS 6 to DSS 8. Conclusions: Human T-lymphotropic virus 1-associated myelopathy/tropical spastic paraparesis is a rapidly disabling disease. Monitoring for HTLV-1 proviral load is recommended in future therapeutic trials.