Natural History of Human T-Lymphotropic Virus 1–Associated Myelopathy

Abstract

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.