Differentiation of HAM/TSP from patients with multiple sclerosis infected with HTLV-I.

Objective: To better differentiate patients with human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) from patients with multiple sclerosis (MS) who are HTLV-I seropositive, we compared the HTLV-I antibodies and HTLV-I proviral DNA loads in CSF and peripheral blood mononuclear cells (PBMC).

Methods: Intrathecal synthesis of HTLV-I antibodies and HTLV-I proviral DNA loads in CSF and PBMC were measured and compared in 39 Brazilian patients: 17 HAM/TSP and 22 HTLV-I-seropositive non-HAM/TSP (7 with other neurologic diseases, 11 asymptomatic carriers, and 4 HTLV-I-seropositive patients with an MS-like phenotype). In addition, we followed immunologic and virologic markers in comparison to the clinical course (by Kurtzke Expanded Disability Status Scale) of seven patients (five with HAM/TSP and two with an MS-like phenotype) for a mean period of 16 (SD +/- 5) months.

Results: The proviral load in CSF and PBMC was higher in HAM/TSP than in non-HAM/TSP patients, except in the two HTLV-I-seropositive patients with an MS-like phenotype that also fulfilled the criteria for HAM/TSP. Higher HTLV-I proviral DNA load in CSF was associated with the higher proviral DNA load in PBMC and lower intrathecal synthesis of HTLV-I antibodies. These laboratory findings remained stable during follow-up.

Conclusion: The high proviral load in peripheral blood mononuclear cells or in CSF or both may be a good marker of human T lymphotropic virus type I (HTLV-I)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) and can differentiate patients with HAM/TSP from patients with multiple sclerosis infected with HTLV-I.