What is HTLV-I associated myelopathy/Tropical spastic paraparesis (HAM/TSP)?
- HAM/TSP is a slowly progressive, chronic myelopathy (disease of the spinal cord) seen in some people infected with the HTLV-1 virus, which results in painful stiffness and weakness of the legs.
Are there other terms used to refer to HAM?
- Chronic progressive myelopathy
- Tropical spastic paraparesis (TSP)
- HTLV-1 associated myelopathy (HAM)
What causes HAM?
- HAM/TSP is caused by infection with the HTLV-1 virus, although the great majority people who test positive for the virus do not go on to get active disease. These individuals are called carriers (see Glossary).
- In some people who are infected with the HTLV-1 virus, inflammation (swelling) occurs in the spinal cord. HAM/TSP is caused by the immune system’s attack on the virus, which involves sending cells called lymphocytes to the affected area of the spinal cord. These lymphocytes release chemicals called cytokines, which not only kill the infected cells but can also cause damage to the nerves. When the immune system's response to the virus causes nerve damage in the spinal cord, the legs gradually lose strength and flexibility.
How do people become infected with the HTLV-1 virus?
- The HTLV-1 virus is transmitted (passed) from an infected person to a non-infected person through bodily secretions and blood. It can be transmitted by sexual contact; via the blood through fresh blood transfusions or through re-use of contaminated needles; or passed from mother to child through breast-feeding.
- You cannot spread HTLV-I by casual contact, such as shaking hands, hugging, and sharing homes and workplace, including bathrooms.
Can HAM/TSP be prevented?
- The transmission of the virus can be decreased through safe sex practices (i.e. condoms or abstinence from intercourse) and avoiding needle sharing. Women who test positive for the virus should not breast feed. Healthcare practitioners should use caution when handling sharp instruments or handling bodily secretions from an infected person.
At what age do the symptoms of HAM/TSP appear?
- The symptoms of HAM/TSP usually appear between the ages of 30 and 50 but may occur earlier. The disease has been known to appear in childhood, but this is very rare. The disease may remain undetected for years after infection begins, but can still be transmitted to another person during this time.
Who gets HAM/TSP?
- An estimated 10-20 million people in the world are infected with HTLV-1. Of those, approximately 0.25-3% of the infected individuals will develop the progressive neurologic disease called HAM/TSP.
- An additional 2% of people infected with the HTLV-1 virus will develop a serious blood cancer (adult T-cell leukemia or lymphoma).
- Although the HTLV-1 virus is present throughout the world, infection with the virus is endemic in some geographical areas -- the Caribbean, southern Japan, areas of Africa that are near the equator, and the Seychelles. Other areas that have a high rate of infection include Central and South America, Melanesia, southern Africa and the northwest coast of Canada. The great majority of infected individuals will never exhibit signs or symptoms of disease.
How is HAM/TSP similar to/different from multiple sclerosis (MS)?
- Many of the symptoms of HAM/TSP are also found in people who have been diagnosed with MS. The clinical course of HAM/TSP is most similar to the primary progressive form of MS (PPMS) in that there is a steady worsening of neurologic functioning, without any distinct relapses (also called attacks) or periods of remission.