Merck Manual

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Tropical Spastic Paraparesis/HTLV-1–Associated Myelopathy (TSP/HAM)


Michael Rubin

, MDCM, New York Presbyterian Hospital-Cornell Medical Center

Last full review/revision Feb 2020| Content last modified Feb 2020
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Tropical spastic paraparesis/HTLV-1–associated myelopathy is a slowly progressive disorder of the spinal cord caused by the human T-lymphotropic virus 1 (HTLV-1).

  • The virus is spread through sexual contact, use of illegal injected drugs, exposure to blood, or breastfeeding.

  • People have weakness, stiffness, and muscle spasms in the legs, making walking difficult, and many have urinary incontinence.

  • To diagnose the disorder, doctors ask about possible exposure to the virus and do magnetic resonance imaging, a spinal tap, and blood tests.

  • Drugs, such as corticosteroids, may help, and spasms are treated with muscle relaxants.

The human T-lymphotropic virus 1 (HTLV-1) is similar to the human immunodeficiency virus (HIV), the virus that causes AIDS. The HTLV-1 virus can cause certain kinds of leukemia and lymphoma (cancers of the white blood cells).

HTLV-1 is transmitted through

  • Sexual contact

  • Use of illegal drugs that are injected into vein (intravenously)

  • Exposure to blood

It can be transmitted from mother to child through breastfeeding. It is most common among prostitutes, injected drug users, people undergoing hemodialysis, and people from certain areas such as those near the equator, southern Japan, and parts of South America.

A similar disorder can result from infection with a similar virus, human T-lymphotropic virus 2 (HTLV-2).

The virus resides in white blood cells. Because the cerebrospinal fluid contains white blood cells, the spinal cord can be damaged. Inflammation develops in the spinal cord and damages the pathways that carry signals about pain, temperature, and position up the spinal cord to the brain and those that carry signals from the brain down the spinal cord to muscles. Damage to the spinal cord results more from the body’s reaction to the virus than from the virus itself.


The muscles in both legs gradually become weak. People may not be able to feel vibrations in their feet and may lose the sense of where their feet and toes are (position sense). Their limbs feel stiff, movements become clumsy, and walking may become difficult. Muscle spasms in the legs are common, as is loss of bladder control (urinary incontinence).

Tropical spastic paraparesis/HTLV-1–associated myelopathy usually progresses over several years.


  • Assessment of the person's risk of being exposed

  • Magnetic resonance imaging

  • Tests to check for the virus in blood and cerebrospinal fluid

The diagnosis of tropical spastic paraparesis/HTLV-1–associated myelopathy is usually based on symptoms and the person’s risk of being exposed to the virus. Thus, a doctor may ask people about their sexual contacts and use of illegal injected drugs.

Samples of blood and cerebrospinal fluid, obtained by a spinal tap (lumbar puncture), are tested for parts of the virus or antibodies to the virus. (Antibodies are produced by the immune system to defend against a particular attacker, such as HTLV-1.)

Magnetic resonance imaging (MRI) of the brain and spinal cord is done to check for abnormalities such as degeneration of the spinal cord and to check for other possible causes of the symptoms.


  • Interferon alfa, immune globulin, and/or corticosteroids

  • For spasms, muscle relaxants

No treatment has been shown to be effective for tropical spastic paraparesis/HTLV-1–associated myelopathy. However, interferon alfa (an antiviral drug), intravenous immune globulin, and/or corticosteroids may slow the progression of the disorder and reduce disability and pain. (Intravenous immune globulin is a purified solution of antibodies obtained from volunteer donors and given by vein.)

Spasms can be treated with muscle relaxants such as baclofen or tizanidine.

Drugs Mentioned In This Article

Generic Name Select Brand Names
Gammagard S/D
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