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HTLV-I-associated myelopathy

Last reviewed dd mmm yyyy. Last edited dd mmm yyyy

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This is a chronic demyelinating disease, resembling multiple sclerosis, which is caused by HTLV-I.

The disease is thought to be an autoimmune reaction as cells of the central nervous system are not infected with HTLV. Tropical spastic paraparesis typically occurs in patients who were infected with HTLV-I during adulthood.

  • HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is characterized by slow progressive spastic paraparesis and positivity for anti-HTLV-1 antibodies in both serum and cerebrospinal fluid (CSF)
    • worldwide, at least 10-20 million people are infected with HTLV-1
    • however, although the majority of infected individuals remain lifelong asymptomatic carriers, approximately 2%-5% develop adult T-cell lymphomas and another 0.25%-3.8% develop HAM/TSP

  • although the mechanisms underlying the development of HAM/TSP are not fully understood, several risk factors are closely associated with HAM/TSP. In particular, HTLV-1 proviral loads are significantly higher in HAM/TSP patients than in asymptomatic carriers and are also higher in genetic relatives of HAM/TSP patients than in non-HAM-related asymptomatic carriers


  • Proietti FA, Carneiro-Proietti AB, Catalan-Soares BC, Murphy EL (2005) Global epidemiology of HTLV-I infection and associated diseases. Oncogene 24: 6058-6068
  • Saito M (2010) Immunogenetics and the Pathological Mechanisms of Human T-Cell Leukemia VirusType 1- (HTLV-1-)Associated Myelopathy/Tropical Spastic Paraparesis (HAM/TSP). Interdiscip Perspect Infect Dis 2010: 478461

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