HTLV-1–associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a slowly progressive viral immune-mediated disorder of the spinal cord caused by the human T-lymphotropic virus 1 (HTLV-1). It causes spastic weakness of both legs. Diagnosis is by serologic and polymerase chain reaction tests of serum and cerebrospinal fluid and MRI. Treatment includes supportive care and possibly immunosuppressive therapies.
(See also Overview of Spinal Cord Disorders.)
The HTLV-1 retrovirus is transmitted via sexual contact, IV drug use, or exposure to infected blood or from mother to child via breastfeeding. It is most common among sex workers, IV drug users, hemodialysis patients, and people from endemic areas such as equatorial regions, southern Japan, and parts of South America.
HAM/TSP affects < 2% of HTLV-1 carriers. It is more common among women; this finding is consistent with the higher prevalence of HTLV-1 infection in women. HTLV-2 may cause a similar disorder.
The virus resides in T cells in blood and cerebrospinal fluid (CSF). CD4+ memory T cells, CD8+ cytotoxic T cells, and macrophages infiltrate the perivascular areas and parenchyma of the spinal cord; astrocytosis occurs. For several years after onset of neurologic symptoms, inflammation of spinal gray and white matter progresses, causing preferential degeneration of the lateral and posterior columns. Myelin and axons in the anterior columns are also lost.
Symptoms and Signs of HAM/TSP
Spastic weakness develops gradually in both legs, with extensor plantar responses and bilateral symmetric loss of position and vibratory sensation in the feet. Achilles tendon reflexes are often absent. Urinary incontinence and urgency are common.
Symptoms usually progress over several years.
Diagnosis of HAM/TSP
Serologic and polymerase chain reaction (PCR) tests of serum and CSF
MRI
HTLV-1–associated myelopathy/tropical spastic paraparesis is suggested by typical neurologic deficits that are otherwise unexplained, particularly in patients with risk factors.
Serum and CSF serologic tests, PCR tests, and spinal cord MRI are indicated. If CSF-to-serum ratio of HTLV-1 antibodies is > 1 or if PCR detects HTLV-1 antigen in CSF, the diagnosis is very likely. Protein and Ig levels in CSF may also be elevated, often with oligoclonal bands; lymphocytic pleocytosis occurs in up to 50% of patients.
MRI shows spinal cord atrophy and T2-weighted images of the lateral columns and anterior nerve roots, which often appear hyperintense on MRI.
Treatment of HAM/TSP
Immunomodulatory or immunosuppressive therapies
Key Points
HTLV-1–associated myelopathy/tropical spastic paraparesis (HAM/TSP) affects < 2% of HTLV-1 carriers and occurs more commonly in women.
Symptoms include gradually developing spastic weakness in both legs, extensor plantar responses, bilateral symmetric loss of position and vibratory sensation in the feet, and absent Achilles tendon reflexes.
Diagnose using serum and CSF serologic tests, PCR tests, and MRI.
