The term “tropical spastic paraparesis” (TSP) has been used for several decades to describe a chronic and progressive disease of the nervous system that affects adults living in equatorial areas of the world. TSP is now called HTLV-1-associated myelopathy (HAM)/tropical spastic paraparesis (TSP). HAM/TSP can cause:

• Progressive weakness
• Stiff muscles
• Muscle spasms
• Sensory disturbance
• Sphincter dysfunction

The cause of HAM/TSP was obscure until the mid-1980s, when a connection was established between the human retrovirus—called “human T-cell lymphotrophic virus type 1” (also known as HTLV-1)—and HAM/TSP. The HTLV-1 retrovirus is thought to cause at least 80 percent of the cases of HAM/TSP by weakening the immune system.

Most people with HAM/TSP have few or no symptoms throughout their lives. In addition to neurological symptoms of weakness and muscle stiffness or spasms, in rare cases individuals with HAM/TSP also may have:

• Uveitis (inflammation of the uveal tract of the eye)
• Arthritis (inflammation of one or more joints)
• Pulmonary lymphocytic alveolitis (inflammation of the lung)
• Polymyositis (an inflammatory muscle disease)
• Infectious dermatitis (inflammation of the skin)
• Keratoconjunctivitis sicca (persistent dryness of the cornea, which is the clear, front “window” of the eye, and conjunctiva, which is the mucous membrane that covers the front of the eye and lines the inside of the eyelids)

The other serious complication of HTLV-1 infection is the development of adult T-cell leukemia or lymphoma. Nervous system and blood-related complications happen only in a very small percentage of people with HAM/TSP.

HAM/TSP is a progressive disease (in other words, it gets worse as time passes), but it is rarely fatal. Most people with HAM/TSP live for several decades after the diagnosis. The outlook improves if they take steps to prevent urinary tract infections and skin sores, and if they participate in physical and occupational therapy programs.

The HTLV-1 virus is transmitted from person to person through infected cells. Transmission can happen through:

• Breast-feeding by mothers who have high levels of antibodies to HTLV-1 in their blood (this is called being “seropositive to HTLV-1”)
• Sharing infected needles during intravenous drug use
• Having sexual relations with a seropositive partner

There is no established treatment program for HAM/TSP. Corticosteroids may relieve some symptoms, but they usually don't change the course of the disorder. Interferon alpha (a pharmaceutical drug) may help for short periods. Interferon beta (a pharmaceutical drug) may improve some aspects of HAM/TSP. Stiff and spastic muscles can be treated with baclofen (Lioresal®) or tizanidine. Urinary dysfunction may be treated with oxybutynin.

• Slowly progressive weakness and spasticity of one or both legs
• Exaggerated reflexes (hyperreflexia)
• Stiff muscles
• Muscle contractions in the ankle (ankle clonus)
• Lower back pain
• A 'weak' bladder and/or urinary incontinence
• Minor sensory changes, especially burning or prickling sensations and loss of vibration sense

Treatment generally aims to control the specific symptoms, as there is no standard treatment available. Interferon alpha may be beneficial over short periods, and some aspects of the disease may be improved with interferon beta. Stiff and spastic muscles may be treated with lioresal or tizanidine, and urinary dysfunction may be treated with oxybutynin.

Corticosteroids were reported to slow progression in one case series and reduce neurologic disability in another. However, others have reported no such benefit with corticosteroids and there have been no randomized clinical trials.