Apoptosis of helper/inducer T-cells were observed in these active inflammatory lesions. Horizontal distribution of inflammatory

lesions was symmetric at all spinal levels and was accentuated at sites with slow blood flow in the middle to lower thoracic levels. HTLV-1 proviral DNA amounts were well correlated with the numbers of infiltrated CD4+ cells. AUY-922 In situ PCR of HTLV-1 proviral DNA and in situ hybridization of HTLV-1 Tax gene demonstrated the presence of HTLV-1-infected cells exclusively in the mononuclear infiltrates of perivascular areas. From these findings, it is suggested that T-cell mediated chronic inflammatory processes targeting the HTLV-1 infected T-cells is the primary pathogenic mechanism of HAM/TSP. Anatomically determined hemodynamic conditions may contribute to the localization of infected T-cells and the formation of main lesions in the middle to lower thoracic spinal cord. Human T lymphotropic PKC inhibitor virus type 1 (HTLV-1) is the first recognized human retrovirus and is found to be a causative agent of adult T-cell leukemia/lymphoma (ATL).1

Epidemiological survey of ATL and HTLV-1 seropositive carriers demonstrated the deviated distribution to southwestern Japan. In 1985, Osame and colleges noticed in one of the most endemic areas of HTLV-1, Kagoshima, that some patients manifesting slowly progressive spastic paraparesis with sphincter dysfunction had antibodies against HTLV-1 in both their sera and CSF. Further analysis of anti-HTLV-1 antibodies on stored

CSF specimens from various neurological diseases found additional cases with slowly progressive spastic paraparesis having anti-HTLV-1 antibodies. Their hematological features did not satisfy diagnostic criteria of ATL. Based on these finding, the term HTLV-1-associated myelopathy (HAM) was proposed as a new clinical entity.2 Independently, Gessain et al. have reported that about 60% of Caribbean patients with tropical spastic paraparesis (TSP) were seropositive for HTLV-1.3 many HAM and HTLV-1-positive TSP were later confirmed as a single clinical entity and the name HAM/TSP was recommended by WHO. HAM/TSP is characterized by a spastic paraparesis with urinary disturbances and anti-HTLV-1 antibody positivity in serum and CSF. Almost all patients show spasticity and/or hyper-reflexia of the lower extremities. Many patients manifest weakness of the lower extremities and a poorly defined (mild) sensory effect. These symptoms are generally slowly progressive, or in some cases static after initial progression, while patients at older ages of onset show faster progression regardless of the mode of transmission. Patients with HAM/TSP have high antibody titers to HTLV-1 both in serum and CSF. Aside from HTLV-1 antibody positivity, other essential laboratory findings include lymphocytic pleocytosis in the CSF and increased CSF neopterin levels. In MRI, high signals on T2-weighted images are observed in the white matter of the brain similar to those found in multiple sclerosis.