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For further information, see CMDT Part 32-03: Other Neurotropic Viruses

Key Features

  • Retroviruses, types 1 and 2, that infect CD4 and CD8 T cells, respectively

  • HTLV-1 infection

    • Associated with HTLV-1 adult T cell lymphoma/leukemia (ATL) and HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP)

    • Infects approximately 20 million individuals worldwide

    • Endemic in southern Japan, Caribbean, much of the sub-Saharan Africa, South America, Eastern Europe, Oceania

  • HTLV-2 is mainly found in native populations of South (1–58%), Central (8–10%) and North America (2–13%), as well as African pygmies tribes

  • Virus is transmitted horizontally (sex), vertically (intrauterine, peripartum, and prolonged breast-feeding), and parenterally (injection drug use and blood transfusion)

  • Transmission via organ transplant has been reported

  • Disease may flare when biologic agents are used for rheumatoid conditions

Clinical Findings

  • ATL presents with

    • Diffuse lymphadenopathy

    • Maculopapular skin lesions

    • Bronchoalveolar disorder

    • Organomegaly

    • Lytic bone lesions

    • Hypercalcemia

  • Opportunistic infections, such as Pneumocystis jirovecii pneumonia and cryptococcal meningitis, are common

  • HTLV-1 seropositivity is associated with

    • Increased risk of tuberculosis and Strongyloides stercoralis hyperinfection

    • Crusted scabies

    • Infective dermatitis

  • HTLV positivity is associated with erythrocytosis, lymphocytosis (HTLV-2) and with thrombocytosis (HTLV-1).

  • HTLV-2 appears to cause a myelopathy that is milder and slower to progress than HAM

  • HTLV-1/HIV coinfection is associated both with higher CD4 counts and a higher risk of HAM

  • Inflammatory states associated with HTLV-1 infection include

    • Arthropathy

    • Recurrent facial palsies

    • Polymyositis

    • Uveitis

    • Sicca

    • Sjögren syndrome

    • Vasculitis

    • Cryoglobulinemia

    • Infiltrative pneumonitis

    • Ichthyosis

  • Bronchioloalveolar carcinoma is increased in frequency in the presence of HTLV-1

  • HAM characterized by

    • Progressive motor weakness

    • Symmetric spastic paraparesis

    • Bilateral facial palsies

    • Falls

    • Nociceptive low back pain

    • Paraplegia with hyperreflexia

    • Bladder and sexual disorders (eg, dyspareunia, erectile dysfunction), sensory disturbances, constipation


  • The peripheral smear can show atypical lymphoid cells with basophilic cytoplasm and convoluted nuclei (flower cells)

  • The diagnostic standard is evidence of clonal integration of the proviral DNA genome into tumor cell

  • Identification of HTLV-1 antibodies supports the diagnosis

  • An HTLV-1 provirus load in peripheral blood mononuclear cells and CSF cells, and an HTLV-1 mRNA load are proposed as markers of HAM risk and progression

  • Serum neopterin levels may indicate disease activity


  • No vaccine or antiviral therapy currently exists for the prevention and treatment of HTLV infections

  • Management of ATL consists mainly of

    • Chemotherapy (such as CHOP and EPOCH regimens), followed by allogeneic stem cell transplantation

    • Immunotherapies are increasingly used, including

      • Monoclonal antibodies (eg, the anti-CCR4 inhibitor mogamulizumab, anti-CD25 agents)

      • SYK/JAK (spleen tyrosine kinase/Janus kinase) inhibitors (eg, cerdulatinib and ruxolitinib)

      • PD-1/immune checkpoint inhibitors (eg, nivolumab)

  • A chemotherapy regimen in Japan using eight different agents shows a higher response rate than traditional biweekly CHOP (40% vs 25%)

  • Combination therapy with interferon-alpha has been used with success. A therapeutic vaccine is in early clinical trials

  • Prophylaxis against infections is needed in ATL because patients show a profound immunodeficiency

  • HAM treated with corticosteroids


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