National Center for Advancing and Translational Sciences Genetic and Rare Diseases Information Center, a program of the National Center for Advancing and Translational Sciences

Human T-cell leukemia virus type 1


Other Names:
HTLV-1; Human T lymphotropic virus type 1
Categories:
Human T-cell leukemia virus, type 1 (HTLV-1) is a retroviral infection that affect the T cells (a type of white blood cell). Although this virus generally causes no signs or symptoms, some affected people may later develop adult T-cell leukemia (ATL), HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) or other medical conditions.[1] HTLV-1 is spread by blood transfusions, sexual contact and sharing needles. It can also be spread from mother to child during birth or breast-feeding. There is no cure or treatment for HTLV-1 and it is considered a lifelong condition; however, most (95%) infected people remain asymptomatic (show no symptoms) throughout life.[2][3]
Last updated: 12/10/2014
Human T-cell leukemia virus, type 1 (HTLV-1) generally causes no signs or symptoms. However, some affected people may later develop adult T-cell leukemia (ATL), HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) or other medical conditions.[1]

Approximately 2-5% of people with HTLV-1 will develop ATL, a cancer of the T-cells (a type of white blood cell). The signs and symptoms of this condition and the disease progression vary from person to person. Affected people may have the following features:[2][3]
  • Fatigue
  • Lymphadenopathy (swollen lymph nodes)
  • Thirst
  • Nausea and vomiting
  • Fever
  • Skin and bone abnormalities
  • Enlarged liver and/or spleen
  • Frequent infections
Roughly .25-2% of people with HTLV-1 will develop HAM/TSP, a chronic, progressive disease of the nervous system. Signs and symptoms of this condition vary but may include:[2][3]
  • Progressive weakness
  • Stiff muscles
  • Muscle spasms
  • Backache
  • 'Weak' bladder
  • Constipation
Last updated: 12/10/2014
Human T-cell leukemia virus, type 1 (HTLV-1) occurs when a person is infected by the human T-cell leukemia retrovirus. HTLV-1 is spread by blood transfusions, sexual contact and sharing needles. It can also be spread from mother to child during birth or breast-feeding. It is unclear why some people with HTLV-1 develop adult T-cell leukemia (ATL), HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP) or other medical conditions, while others remain asymptomatic (show no signs or symptoms) their entire lives.[2][3]
Last updated: 12/10/2014
Human T-cell leukemia virus, type 1 (HTLV-1) is usually diagnosed based on blood tests that detect antibodies to the virus. However, HTLV-1 is often never suspected or diagnosed since most people (95%) never develop any signs or symptoms of the infection. Diagnosis may occur during screening for blood donation, testing performed due to a family history of the infection, or a work-up for an HTLV-1-associated condition such as adult T-cell leukemia (ATL) or HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP).[2][3]
Last updated: 12/10/2014
No cure or treatment exists for human T-cell leukemia virus, type 1 (HTLV-1). Management is focused on early detection and preventing the spread of HTLV-1 to others. Screening blood doners, promoting safe sex and discouraging needle sharing can decrease the number of new infections. Mother-to-child transmission can be reduced by screening pregnant women so infected mothers can avoid breastfeeding.[4][2]
Last updated: 12/10/2014
Ninety-five percent of people with human T-cell leukemia virus, type 1 (HTLV-1) never have any signs of symptoms of the infection and do not go on to develop medical problems.

Approximately 2 to 5% of infected people will develop adult T-cell leukemia (ATL). Depending on the subtype of ATL, people usually live an average of 6 months to 2 years following diagnosis. Although chemotherapy can produce a complete remission, it does not alter the life expectancy.

About .25 to 2% of people with HTLV-1 infection will develop HTLV-1 associated myelopathy/tropical spastic paraparesis (HAM/TSP). People with HAP/TSP are often unable to walk unassisted within 10 years of onset and need to use a wheelchair within 21 years.[3]
Last updated: 12/10/2014

Research helps us better understand diseases and can lead to advances in diagnosis and treatment. This section provides resources to help you learn about medical research and ways to get involved.

Clinical Research Resources

  • ClinicalTrials.gov lists trials that are related to Human T-cell leukemia virus type 1. Click on the link to go to ClinicalTrials.gov to read descriptions of these studies.

    Please note: Studies listed on the ClinicalTrials.gov website are listed for informational purposes only; being listed does not reflect an endorsement by GARD or the NIH. We strongly recommend that you talk with a trusted healthcare provider before choosing to participate in any clinical study.

These resources provide more information about this condition or associated symptoms. The in-depth resources contain medical and scientific language that may be hard to understand. You may want to review these resources with a medical professional.

Where to Start

  • The National Cancer Institute provides the most current information on cancer for patients, health professionals, and the general public.
  • The National Organization for Rare Disorders (NORD) has a report for patients and families about this condition. NORD is a patient advocacy organization for individuals with rare diseases and the organizations that serve them.

In-Depth Information

  • Medscape Reference provides information on this topic. You may need to register to view the medical textbook, but registration is free.
  • PubMed is a searchable database of medical literature and lists journal articles that discuss Human T-cell leukemia virus type 1. Click on the link to view a sample search on this topic.

Selected Full-Text Journal Articles

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  • Is there treatment or a cure for HAM/TSP or for HTLV-1 in general? See answer


  1. David T Scadden, MD; Andrew R Freedman, FRCP; Paul Robertson, MRCP. Human T-lymphotropic virus type I: Virology, pathogenesis, and epidemiology. UpToDate. June 2014;
  2. HTLV Type I and Type II. NORD. May 2012; http://www.rarediseases.org/rare-disease-information/rare-diseases/byID/1203/viewAbstract.
  3. Ewa Maria Szczypinska, MD. Human T-Cell Lymphotropic Viruses. Medscape. August 2014; http://emedicine.medscape.com/article/219285-overview.
  4. David T Scadden, MD; Andrew R Freedman, FRCP; Paul Robertson, MRCP. Human T-lymphotropic virus type I: Disease associations, diagnosis, and treatment. UpToDate. March 2014;